Denim Washing. Terminologies, Technologies, and Sustainability Issues

Livre Spécialisé , 2021 , 167 Pages

Ingénierie - Génie chimique

This book is written focusing on the process of denim washing, which is one of the vital stages for producing fashionable and comfortable denim items. This book is not to provide detailed knowledge regarding denim washing; however, it will certainly be conducive for primary learners to understand the basic concepts, available washing technologies, and their sustainability issues.

In fact, in this book, a chapter entitled "Terminologies of Denim Washing‘ is presented so that primary readers can be introduced to different terms related to the denim washing process. Besides, a chapter entitled "Cutting Edge Technologies‘ is presented in this book and will hopefully be beneficial for academicians to know the different types of modern concepts on denim washing, even though details are not targeted in this work.

Denim is a world-renowned textile with a significant added value. Twill weave, indigo-dyed warp, and white weft yarns are used to make this fabric. It is one of the world's oldest fabrics and is worn by people of all ages. Because modern consumers want apparel that not only looks nice but also feels well, a variety of treatment processes are utilized to finish denim fabrics, striving for new conceivable fabric appearance and comfort effects. One of the most significant finishing steps for denim items is washing, which gives them a worn look and a softer hand. This work describes the historical background of denim and denim washing. Besides, the significance and limitations of denim washing are also presented. Finally, future aspects of denim washing are mentioned in brief.

Contents

Preface

1 Concept of Denim Washing
1.1 Introduction to Denim
1.2 History of Denim Washing
1.3 Significances of Denim Washing
1.4 Limitations of Denim Washing
1.5 Future of Washed Denim
1.6 References

2. Washing Process
2.1 Introduction to Washing Process
2.2 Washing Cycle
2.3 Pre-treatment (De-sizing)
2.4 Washing Machine
2.4.1 Horizontal Washing Machine
2.5 Hydro Extractor
2.6 Tumble Drying
2.7 Pressing
2.8 Various Types of Washing Method
2.9 Basic Process Flow Chart
2.10 Machineries of Washing Plant
2.11 Required Chemicals
2.12 Flow Chart of Different Washing Methods
2.13 References

3. Terminologies of Denim Washing

4. Laser Washing
4.1 Introduction to Laser Washing
4.2 Principle of Laser Technology
4.3 Laser Based Denim Fading
4.4 Software for Laser Fading
4.4.1 File Types
4.5 Laser Patterns
4.6 Influencing Factors of the Laser Treatment
4.7 Advantages of Laser Finishing
4.8 Disadvantages of Laser Washing
4.9 Machinery for Laser Finishing
4.9.1 Laser Blaze
4.9.2 Multicolour Laser Technology
4.9.3 Jeanologia’s Laser Technology
4.9.4 Arges Laser System
4.9.5 F.L.X. technology
4.9.6 Renowned Companies
4.10 References

5. Cutting Edge Technologies
5.1 Introduction
5.2 e-Flow technology
5.3 Enzyme Spray technology
5.4 Techno flow Twin Technology
5.5 Robotic Technology
5.6 Tonello’s Washing Technology
5.6.1 ECOfree: new Ozone washing system
5.6.2 NoStone®+ System
5.6.3 Core Technology
5.6.4 UP Technology
5.6.5 All-in-One System
5.6.6 OBleach
5.6.7 BATIK Technology
5.7 Xeros Washing Technology
5.7.1 XOrbsTM
5.7.2 XDrum™
5.7.3 XFiltra™
5.7.4 Benefits of Xeros Washing Technology
5.8 Jecostone System
5.9 Aqualess Mission Technology
5.10 Smart Bleach Technology
5.11 Smart Foam Technology
5.12 Denethic Technology
5.13 Oxygene Technology
5.14 Washpro Technology
5.15 References

6. Sustainability Issues
6.1 Introduction
6.2 Methods for Achieving Sustainability
6.3 Sustainability Issues of Conventional Denim Washing
6.3.1 Sandblasting
6.3.2 Stone Washing
6.3.3 Bleaching Wash
6.3.4 Potassium Permanganate (PP) Spray Washing
6.3.5 Enzymatic Stoning Wash (Bio-stoning)
6.4 Sustainability Issues of Latest Denim Washing
6.4.1 Enzymatic Wash
6.4.1.1 Laccases
6.4.1.2 DeniLite® Cold
6.4.2 Combined Washing Concept
6.4.3 Nostone®+
6.4.4 Potassium Permanganate Alternatives
6.4.4.1 OrganIQ Product
6.4.4.2 Nearbleach Sky White
6.4.5 Ozone Washing 6.4.6 Nanobubble e-Flow Technology
6.4.7 Water Jet Fading
6.4.8 Laser Technology
6.4.9 Plasma Treatment
6.5 Sustainability Issues of Digitally Printed Denim
6.6 Software for Measuring Sustainability in Washing
6.6.1 Environmental Impact Measuring (EIM) Software
6.6.2 Environmental Score (eScore) Software
6.7 Conclusion 6.8 References

7. Testing Principles of Washed Denim Khan MKR, Begum HA
7.1 Significance of Washed Denim Testing
7.2 Tear Strength
7.2.1 Dynamic Tear Test
7.3 Tensile Strength
7.3.2 Grab Test
7.4 Dimension Stability
7.4.1 Dimension Stability Testing
7.4.1.1 Dimensional Stability to Washing
7.4.1.2 Distortion or Skewness after Wash (Torqueing)
7.5 Color Fastness
7.5.1 Color Fastness to Wash Test
7.5.2 Color Fastness to Rubbing (Crocking) Testing
7.5.3 Color Fastness to Perspiration Testing
7.5.4 Color Fastness to Light Testing
7.5.5 Phenolic Yellowing Testing
7.6 Determination of pH Value
7.7 Light Sensitive Fabric (LSF) Test
7.8 Appearance Test after Wash
7.9 References

Preface

The demand for denim clothes is increasing worldwide, with more being produced than any other type of fabric in the current world. Consequently, denim industries are emerging as a vital part of the textile sector in the world, demanding available books on the subject of denim manufacturing so that students, technicians, and other relevant employees can easily comprehend the various processes related to the denim industry. From that perspective, this book is written focusing on the process of denim washing, which is one of the vital stages for producing fashionable and comfortable denim items. This book is not to provide detailed knowledge regarding denim washing; however, it will certainly be conducive for primary learners to understand the basic concepts, available washing technologies, and their sustainability issues. In fact, in this book, a chapter entitled "Terminologies of Denim Washing’ is presented so that primary readers can be introduced to different terms related to the denim washing process. Besides, a chapter entitled "Cutting Edge Technologies’ is presented in this book and will hopefully be beneficial for academicians to know the different types of modern concepts on denim washing, even though details are not targeted in this work.

In this book, only a few machine manufacturers are mentioned, although many machine manufacturers are available on the market. However, no responsibility is admitted in case any inadvertent error or incorrectness is noticed therein. It would be a great work if any error is addressed to the author. Of course, the author is limited in terms of knowledge, hoping to be corrected in the next edition. Besides, it is acknowledged that several images are used in this book with citing references; indeed, the author is wholeheartedly grateful to those references. The author is hugely indebted to his family members for their unbelievable support, making it possible to complete this book. Finally, the author’s attempt will be meaningful if readers themselves benefit from this little work.

Md. Khalilur Rahman Khan

Acknowledgement

Foremost, the author would like to acknowledge Engineer Manzur Murshed (25th Batch, BUTEX) who inspired me to finish this book. Special thanks to him for his precious time in reviewing individual chapters along with his suggestions on the benefits of this book in the textile field. Acknowledgement would be incomplete without stating the work experience of Manzur Murshed in the denim sector. He has seventeen years of experience in denim finishing. He worked for several companies, which included Gap Inc., Ha-Meem Group, Armana Group, Hams Group, and so on. Currently, he is the Chairman of ‘Eurovintage Fashion BD Limited," working to export vintage-look garments. In fact, his review of this book was really significant.

I would like to thank Sohanur Talukder Sagar (34th Batch, BUTEX), who is working as Head of Washing at Hams Washing & Dyeing Ltd., for sharing his excellent practical knowledge regarding denim washing, which was really conducive while writing this book.

Special thanks to Dr. Hosne Ara Begum (Professor, BUTEX), who always inspires me in the way of my learning. In fact, she contributed in writing to Chapter 7, entitled "Testing Principles of Washed Denim."

Finally, there are also people who have inspired me on this subject while preparing the manuscript. This must include Engineer Shamim (30th Batch, BUTEX), Engineer Sayem (18th Batch, BUTEX), Engineer Tamim (33rd Batch, BUTEX) and Hafiz. In fact, they need credit for inspiring me to write this book.

Dedicated to my beloved son, Nasafi, and my parents

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1.Concept of Denim Washing

Denim is a world-renowned textile with a significant added value. Twill weave, indigo-dyed warp, and white weft yarns are used to make this fabric. It is one of the world's oldest fabrics and is worn by people of all ages. Because modern consumers want apparel that not only looks nice but also feels well, a variety of treatment processes are utilized to finish denim fabrics, striving for new conceivable fabric appearance and comfort effects. One of the most significant finishing steps for denim items is washing, which gives them a worn look and a softer hand. This chapter describes the historical background of denim and denim washing. Besides, the significance and limitations of denim washing are also presented. Finally, future aspects of denim washing are mentioned in brief.

1.1 Introduction to Denim

No other traditional textile product has been more widely accepted and used by people of different cultures, genders, ages, and origins than denim fabric throughout history. Denim is a robust cotton twill fabric in which the weft threads pass beneath two or more warp threads. Only the warp threads are dyed in blue denim, while the weft threads are left white. One side of the cloth shows the blue warp threads, while the other side exposes the white weft threads as a result of the warp-faced twill weaving. Indigo, vat, and sulphur dyes are typically used to color denim, and indigo accounts for 67 percent of total shares. Fashion dyeing in denim is done with indigo dyes. Jeans are a popular cotton casual clothing item produced from denim all around the world because of its benefits, which include a unique worn appearance [1-3].

Denim is an Americanization of the French term "serge de Nimes," a fabric that dates back to the Middle Ages and originated in Nimes, France. In 1789, a Rhode Island newspaper reported on local denim production, which was one of the first times the word "denim" was used. Then, in 1792, a book called "The Weavers' Draft Book and Clothiers Assistant" published technical sketches of various denim weaving procedures. Webster’s dictionary adopted the brief term "denim" as the English version of denim in 1864. Jeans, dungarees, and Levi's are all words that are connected. Jeans are rooted in the cotton trousers worn by Italian sailors from Genoa; the term "jeans" is French, as the French refer to Genoa and its inhabitants as "Genes." Jeans have always been in style around the world. Historians, teenagers, and movie stars have all had strong opinions about this cloth, which has evolved over time into many styles. Dungarees are derived from the Hindi word "dungr," which means "coarse fabric." This phrase is most commonly used to describe blue denim fabric or denim-like trousers. The term "Levi" belongs to Levi Strauss, one of the most well-known denim companies in the world [1, 3-5].

Denim is still a popular choice for attractive and long-lasting clothing, but it wasn't always a fashion statement. This fabric was designed to resist the challenges of the workplace, and it has developed from useful work wear to fashionable statement wear over time. Denim, although being one of the oldest materials in the world, is still fashionable today. Since its inception, it has always been made of cotton. Because denim is a unique piece of clothing that appeals to people of all ages, a lot of research and development has gone into it in the last few decades 6. Among all textile items, denim has the most widespread appeal. It has had a significant social and cultural impact on consumers 7. Denim is now a multibillion-dollar industry with numerous subcategories. Denim products can be found in every retail channel, with prices ranging from under ten dollars to hundreds of thousands of dollars. Pants, skirts, shirts, shorts, jackets, caps, bags, upholstery, wall coverings, and bed linens are just a few of the fiber things that may be manufactured from denim fabric. As a result, denim fabrics come in a variety of weights (as determined by yarn count and fabric density, warp per inch, and filling per inch). Denim fabric weights typically range from 5 to 16 oz/yd2. Light denim will work well for dresses or shirts that require drape, softness, and flexibility. Blue jeans, pants, and skirts are often made from heavy denim weighing 10 to 15 oz/yd2. The majority of denim fabric is made of cotton fibers, but a significant portion is made of cotton blended with other fibers in various blend ratios. The majority of yarns used in denim fabric are open-end or rotor-spun, while ring-spun or compact yarns account for a significant portion of the fabric. In the same denim fabric, a mix of ring spun and open-end spun yarns can be utilized [1, 5].

Denim clothing is becoming more popular around the world, with the United States, Italy, and Japan emerging as the most promising markets for denim jeans. As denim is manufactured more than any other form of cloth in the modern world, denim mills are investing more money than they have in the past in developing new denim concepts, which means that all jeans makers will experiment with and reach new degrees of finishing [6,8,9].

1.2 History of Denim Washing

As buyer satisfaction levels fluctuate over time, softness, comfort, and fading illusion play an increasingly important part in denim finishing. Denim washing is a dynamic aspect of the day-to-day runway when it comes to comfort, performance, and a trendy cool feeling 10. Pre-washing, which was established in Japan in the 1970s, is the most basic and oldest technology in the denim industry. After World War II, pre-owned US military jeans began to be sold in Japan in the 1940s. They were worn in and had faded to a pale blue color, but they were still sturdy. People in Japan quickly became enamored with its durability, softness, and pleasant light color. Because pre-worn jeans were the only ones accessible at the time due to trade restrictions, they assumed that was how all the jeans were created. When the Japanese government relaxed the limitations and raw jeans began to be imported from the United States, Japanese denim fans were horrified by the raw denim's poor fastness, stiff feel, and excessive shrinkage. Unwashed jeans were not well welcomed on the market. In the 1960s, a couple of Japanese companies began producing raw jeans in Japan, but they ran into the same issues as the American raw denim. Manufacturers addressed challenges in order to meet the needs of consumers. They came up with the notion of pre-shrinking and washing brand-new jeans before they shipped to retailers in the 1970s to remove any lingering extra indigo and wax on denim and improve the denim's fastness and feel. To give them a pre-wash in quantity, they cooperated with dry cleaners in Tokyo and dying houses in Okayama. As a result, their jeans were lovely and soft, and they didn't have to worry about color migration or significant shrinkage. They seized the hearts of denim aficionados in Japan. Since then, jeans are usually laundered before being sold all over the world. Following this breakthrough, Japanese denim manufacturers developed further washing procedures in order to produce high-quality jeans. There were only two techniques to pre-wash jeans at first: rinsing and bleaching. However, since its inception in the 1970s, denim washing has been a constantly changing aspect of the denim business 11.

1.3 Significances of Denim Washing

Today, a garment's style and longevity are no longer the only factors to consider; it's also important to consider how comfortable it is to wear. Denim clothing, in fact, places a premium on comfort and fit. During use, clothing that comes into intimate contact with the human body engages with the skin in a constant and dynamic manner. Mechanical, optical, and thermal feelings are stimulated as a result of this interaction involving clothes and the human body, resulting in either comfort or discomfort assessment. The key factors impacting clothing comfort are fiber type, yarn qualities, fabric construction, finishing techniques, and clothing conditions 6. Another important factor that influences consumers' clothing choices is fashion. Denim, on the other hand, is a tough, stiff, and long-lasting fabric. Denim is traditionally a fabric with a high mass per unit area, making it a high density fabric [9,12,13]. Because of its impacts on appearance and comfort, denim garment (Jeans) washing is one of the most extensively utilized finishing processes. Furthermore, because denim makes up the majority of washed garments, the term "wash" has evolved to refer to the process of completing denim garments 14. Denim is typically dyed at the yarn stage before being woven together with dyed and undyed yarns that are each treated with a sizing ingredient for tenacity. The majority of the 'raw' denim fabric produced is a dark color that is later treated to get the desired effect. This allows for more tone contrasts and flexibility in subsequent treatments 15. Denim is generally uncomfortable to wear without washing because of the weaving and dyeing effects. It requires a finishing process to make it softer, suppler, and smoother, which will improve the wearer's comfort. As a result, garment washing is a revolutionary procedure for imparting a worn-out look, modifying the appearance, and improving the clothes' comfort capabilities. The popularity of garment washing, particularly of washed denim (shown in figure 1.1), has been steadily expanding in the global market [13, 16]. Performing the denim washing has a number of advantages. The following 17 are noteworthy:

- By removing size components from the fabric, it becomes softer to the touch.
- Softness can be improved by using a softener at the end of the washing.
- Dirt, stains, impurities, gum, and other contaminants that may have formed in the clothes during production could be eliminated.
- Shrinkage may occur during the washing process; however, there is no chance of this causing a problem afterward.
- A faded or worn-out effect could be added to the items, creating a new look.
- Different washing processes can produce a similar appearance.
- The cost of starting a washing plant is low, which necessitates less land space and lower staff costs.

Abbildung in dieser Leseprobe nicht enthalten

Figure-1.1 Washed Denim Items.

1.4 Limitations of Denim Washing

Because this operation is typically used on clothes that have already been sewn, it is critical to understand the influence of specific washings on fabric in attempt to uphold the quality of a sewing garment. Washing process not only alters their aesthetic look of denim products but also deteriorates in their structural and mechanical capabilities, particularly their strength and durability. Items are influenced by a complex of diverse components throughout the washing cycle, including a washing solution, abrasion, creasing, heat, various chemicals, and so on. As a result, extensive degradation of the polymers that make up fibers occurs, resulting in extensive wear of the products. Fabrics from short fibers are more prone to wear and tear because fibers are gradually removed throughout the washing process. Zippers can be severely damaged by washing processes, and denim durability suffers as a result. Furthermore, shrinkage qualities of the cloth cause size changes. The size change of the clothing is directly related to the amount of shrinkage characteristics of the fabric [9, 17.18].

Textile industries, on the other hand, are concerned about maintaining high levels of performance and production, so they wash their jeans at the lowest possible cost, regardless of the environmental and human consequences. Textiles and apparel, especially denim production, have a substantial environmental impact at various phases of the life cycle, with washing stages playing a key role. Denim/jeans are still the most polluting textile items on the planet, because to indigo dyeing, chemicals, and the amount of water required to achieve the greatest washes. In fact, because of the large volume of water and chemicals used, the washing sector is considered a major industrial waste generator [19-20]. Denim is commonly dyed using indigo, which is difficult to degrade or remove using physical or chemical methods. Indigo is regarded as a hazardous chemical for the environment due to the development of poisonous aromatic amines in wastewater 21. Furthermore, other substances such as surfactant, laundry detergent, chlorine, sodium thiosulfate, and fatty acids pollute the water during denim washing. Denim wet finishing discharges 80% of effluents into local water sources, posing health, environmental, and climate-related risks. As a result, the use of environmentally friendly, nontoxic, entirely biodegradable ingredients in current denim finishing processes is gaining popularity [10,20].

1.5 Future of Washed Denim

Denim is both fashionable and functional. Denim is the most fashionable and favored dress among the new generation in terms of fashion. Denim jeans are a classic piece of clothing. Because of the global development of denim culture, the denim industry is booming. It has carried with it a trend of fast-changing fashion all throughout the world. Wash is essential for denim since it adds style and creates new fashion trends. In fact, one of the most significant aspects of creating beautiful denim is the washing process, which is crucial in the denim chain due to the numerous impacts that customers want on their jeans. As a result, denim washing has become one of the most essential manufacturing channels for addressing the fashion market's ever-changing demands. Denim's once-vast mass market has been split, fragmented, and splintered into a plethora of mini, micro, and specialized markets. A large number of brands to choose from, a different perception of the cult value of owning small insider labels, and an obsessive loyalty exclusively to what is fashionable on a daily basis have all shaped the last generation. Denim, free of all societal and creative constraints, may now be worn in a variety of disguises and circumstances, and it has broken through practically every price barrier. However, denim jeans are one of the most water-intensive, hazardous, and energy-intensive textiles in fashion. Simultaneously, circular economy and fashion sustainability are the actual subjects for the upcoming future of denim washing, as the concept of sustainability is continuously developing. Consequently, this method has changed dramatically in recent years, owing to environmental, sustainable, health and safety, and fashion concerns. Technological innovations are continually increasing in order to reduce its influence. Some of the modifications include the removal of stones, the employment of enzymes, the dramatic reduction of water and energy, the purging of chemical products and the entrance of ozone finishing, and the increased use of laser treatments. Denim washing processes will be improved more and more in the coming years, meeting the desire for sustainable fashion while keeping the environment in mind. Washed denim has the potential to open new markets and frontiers for the denim industry by incorporating novel washing procedures and better performance.

1.6 References

1. Yehia E. Elmogahzy, Engineering Textiles: Integrating the Design and Manufacture of Textile Products, Chapter-13: Performance characteristics of traditional textiles: Denim and sportswear products, Second Edition © 2020 Elsevier Ltd.
2. Ahamed, J., Mahmud, Md.F., Ahammed, M.F., Mia, R., Hasan, Md.Z., Khan, T.H., Limon, G.Q. and Shamim, A.Md. (2021) Evaluate the Strength of Denim Goods Using Different Washing Technique. Journal of Materials Science and Chemical Engineering, 9, 1-8. https://doi.org/10.4236/msce.2021.93001
3. yu, Yuanyuan & Jiugang, Yuan & Wang, Quandou & Fan, Xuerong & Ni, Xiaoyan & Cui, Li. (2013). Cellulase immobilization onto the reversibly soluble methacrylate copolymer for denim washing. Carbohydrate polymers. 95. 675-80. https://doi.org/10.1016/j.carbpol.2013.03.043
4. Du W, Gosh RC, Zuo D-Y, Zou H-T, Tian L, Yi C-H. Discoloration of Cotton/Kapok Indigo Denim Fabric by Using a Carbon Dioxide Laser. FIBRES & TEXTILES in Eastern Europe 2016; 24, 4(118): 63-67. DOI: 10.5604/12303666.1201132
5. L. Downey, A Short History of Denim, (PDF). Official Levi Strauss & Co. Historian, https://www.levistrauss.com/levis-history/, 2007
6. Gokarneshan, Narayanan. (2018). Exploring the Versatility of Denim Fabrics - A Review of some Significant Insights on Recent Researches. Current Trends in Fashion Technology & Textile Engineering. 2. 10.19080/CTFTTE.2018.02.555592.
7. Patra, A.K., Madhu, A. & Bala, N. Enzyme washing of indigo and sulphur dyed denim. Fash Text 5, 3 (2018). https://doi.org/10.1186/s40691-017-0126-9
8. Y.I.L. Kwok, Anthony S.W. Wong, Y.I. Li, Xin Zhang, chapter 20 - Sensory comfort of denim product, Editor(s): Y. Li, A.S.W. Wong, In Clothing Biosensory Engineering, Woodhead Publishing, 2006, Pp. 335-349, https://doi.org/10.1533/9781845691462.335.
9. Hoque, Md. Saiful & Abdur Rashid, Muhammad & Chowdhury, Sushmita & Chakraborty, Aishila & Haque, Abu Naser Md. Ahsanul. (2019). Alternative Washing of Cotton Denim Fabrics by Natural Agents. 79-83. 10.11648/j.ajep.20180706.12.
10. Mohammad Abul Hasan Shibly, Mohammad Mohsinul Hoque, Solayman Miah, Development of Eco-friendly Denim Fabric Washing by Natural Resources, International Journal of Textile Science, Vol. 10 No. 1, 2021, pp. 1-6. doi: 10.5923/j.textile.20211001.01.
11. Michi Nakai, The History of Jeans Finishing; Pre-washing, November 11, 2019, Retrieved from http://fashionpathfinder.tokyo/?p=10129
12. Burcu Sancar Beşen & Onur Balcı (2016) Fading of Cotton Yarn Colored with C. I. Vat Blue I (Indigo Dye) via Ozone Application, Ozone: Science & Engineering, 38:5, 395-409, DOI: 10.1080/01919512.2016.1204529
13. Değırmencı Z. Study on the Loss of Strength of Denim-like Knitted Fabrics after Different Washing Treatments. FIBRES & TEXTILES in Eastern Europe 2017; 25, 3(123): 98-105. DOI: 10.5604/01.3001.0010.1697
14. Dr. Csanák, edit. (2014). Sustainable concepts and eco-friendly technologies in the denim industry. 10.13140/rg.2.1.3783.0484.
15. Retrieved From https://www.scribd.com/document/421834633/Tonello-Tusuka-Washing-Ltd-pdf
16. Mondal, M.I.H., Khan, M.M.R. Characterization and process optimization of indigo dyed cotton denim garments by enzymatic wash. Fashion and Textiles 1, 19 (2014). https://doi.org/10.1186/s40691-014-0019-0
17. Vishnu Pareek, Shrikant Eklahare, Denim washing: Its process cycle, Feb 2014, Indian Textile Journal. Available from https://indiantextilejournal.com/articles/FAdetails.asp?id=5894
18. Juciene, Milda & Dobilaite, Vaida & Kazlauskaite, G.. (2006). Influence of industrial washing on denim properties. Materials Science. 12. 355-359.
19. Sarra Ben Hmida & Neji Ladhari (2015): Study of Parameters Affecting Dry and Wet Ozone Bleaching of Denim Fabric, Ozone: Science & Engineering, DOI: 10.1080/01919512.2015.1113380
20. Shamsuzzaman, M., Kashem, M., Sayem, A. M., Khan, A., Shamsuddin, S., & Islam, M. (2021), Quantifying environmental sustainability of denim garments washing factories through effluent analysis: A case study in Bangladesh, Journal of Cleaner Production, Volume 290, https://doi.org/10.1016/j.jclepro.2020.125740.
21. Montazer, Majid & Sadeghianmaryan, Ali. (2008). Application of Laccases with Cellulases on Denim for Clean Effluent and Repeatable Biowashing. Journal of Applied Polymer Science – J. Appl. Polym Sci. 110. 3121-3129. 10.1002/app.28920.

Washing Process

Denim washing procedures have become a crucial component of the denim industry and have established a cornerstone of fashion impact. Different washing strategies are used to achieve the desired effect (for example, a vintage look) as well as comfort. Descriptions of industrial washing machines and a list of other ancillary machinery are addressed in this chapter. In addition, a list of chemicals used in denim washing, as well as their basic functions, is briefly discussed.

2.1 Introduction to Washing Process

The washing process plays a significant part in denim production because of the numerous effects on denim clothes that consumer so demand. Denim has been able to maintain its current prominence as a symbol of modeling and modern culture thanks to many sorts of washing processes. Manufacturers are constantly searching for new washing strategies as denim washing has become a cornerstone of fashion effects. Denim garment discoloration and making it comfortable to handle are the two basic goals of denim fabric washing 1. The worn-down appearance by stripping the indigo dye from the fiber surface selectively, a denim garment can be made. Denim clothing with a worn, distressed appearance is in high demand. It can be done either before or after the fabric is made up or after the apparel is finished. It confers a softer appearance on denim fabric. Typically, denim is turned in a barrel machine or washing machine with a perforated drum containing stones or chemical detergents and water for one or two hours [2-4].

Denim fabric's weft yarns are generally white, while the warp yarns are indigo-dyed. Natural worn-out or wash-out effect only occurs with denim fabric manufactured with warp yarns that has ring effect dyeing (i.e., perimeter dyeing), dyed with indigoid vat dye. Ring dyeing is a term that refers to the paucity of dye penetration all the way to the center of the yarn. The majority of dyes are stained on the fiber surface, forming a dye layer there, whereas only a few colors are partially diffused into the fiber core. As a result, a ring-like appearance of the dye can be seen cross-sectionally around the fiber, hence the phrase "ring dyed". The coating of this ring-like dye prevents further dye diffusion. After that, the dyed warp yarns are weaved with the filler yarns, which are un-dyed yarns (or weft). This dyeing causes dyed fabric to lack its wash and rubbing fastness, as well as other staining-related fastness attributes. The white core of the garment is revealed when it is abraded, either by normal use or by a garment washing process, and it influences the overall color and texture of the garment, offering denim a distinctive look that develops with age 5.

New mechanical (dry) and chemical (wet) impacts for denim clothing have been created in recent years. Dry process refers to a method that is applied to denim clothes while they are dry, whereas wet process refers to a process that is performed when they are wet. A vintage denim feel can be achieved by blending a number of unique and individual looks in each pair of jeans. Effects like resin whiskers, accent abrasion, and color discharge, for example, can be combined to obtain the desired result. The requirement for a competitive strategy in order to provide value is the driving reason for change in denim washing. The use of diverse methods of denim washing is predicted to yield innovative and improved results, as well as increased financial profits.

2.2 Washing Cycle

The process starts when loomstate denim — that is, denim that has not yet been finished — moves through a number of procedures, most of which include approaches that age or add distinctive effects to denim clothes. They can be washed right away or desized before being washed. After the procedure is finished, the jeans are unloaded and sent to a softening area. Finally, the jeans are pressed, inspected, and packaged for shipment after drying.

2.3 Pre-treatment (De-sizing)

This is the most fundamental, but crucial, stage in the washing process. In relation to the final goal, specialists must take the proper precautions in this section. This technique has three major goals: eliminating impurities from the fabric, de-sizing, and reducing the possibility of creases on the garment. Significantly, desizing denim is required to remove the sizing compounds added to the indigo warp strands prior to weaving. Different types of desizing agents are used in denim washing, including detergents, enzymes, high alkaline, high acids, and oxidative chemicals, which are chosen based on compatibility, price, advantages, disadvantages, and availability.

2.4 Washing Machine

Denim washing's resource intensity is eventually determined by two factors: the intended end product and the techniques employed to achieve it. When it comes to the former, it's a given that products that need to have a more worn appearance and feel will involve more intensive processing than those that are closer to their natural state. When it comes to processing, the efficiency is determined by both the machinery and the inputs utilized in the wash. There are two types of washers: front loading and belly washers. The former is considered the more modern of the two, because it uses significantly less water than the older belly washing machines 6.

2.4.1 Horizontal Washing Machine

The washing machine is also called as clothes washer or simply the washer. The horizontal-axis design is used in the majority of commercial and industrial washing machines around the world. A fixed outer drum and a revolving inner drum with tiny holes around the edge are used (shown in figure 2.1). A horizontal axis washing drum is frequently incorporated in the overall architecture of a front-loading washing machine, and loading is performed through a door on the front side of the machine. At the entrance, a translucent window is typically, but not always, present. The cylinder's back-and-forth motion, as well as gravity, provide agitation. The inner drum can be separated into three or four pockets, or buffle plates can be fitted. The clothing are raised up and then dropped by buffle plates on the inside wall of the drum. The fabric weave flexes, allowing water and chemicals to pass through a load of garments. The fabric is moistened with less water because the wash operation does not require the clothing to be freely suspended in water. The tumbling's repetitive dropping and folding movement can easily generate a lot of foam or suds. To prevent water from dripping onto the floor during the wash cycle, the outside drum, unlike the inside drum, must be entirely watertight. Because opening the door while the machine is in use could result in water rushing out onto the floor, this access door is secured shut with an interlocking device for the duration of the wash cycle. It's easy to pinch the fabric between the door and the drum on front-loaders without watching windows on the door, causing shredding and damage to the pinched clothing during tumbling and spinning. The main benefit of this sort of rotary drum machine is that it uses very little water to run [7, 8]. For bulk clothing, front loading and top loading washing machines are typically employed. The primary distinction between a front loading and a top loading washing machine is how the cloths are loaded. A front loader relies on gravity and side-mounted paddles to agitate the clothes. The advantages of a front-loading machine are numerous. The capacity of a front-loading washing machine is one of its advantages. The horizontally oriented drum can accommodate at least 20% to 30% more clothing per load. Fewer loads frequently equates to lower utility bills. These high-efficiency machines use less water and have a lower environmental effect because they save both water and electricity. Moreover, a front loading washing machine removes more water during the final spin cycle. This generally correlates to faster drying periods, resulting in electricity savings. Though they are efficient and effective, but they are assumed to be expensive.

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Figure-2.1. Basic Construction of Horizontal Washing Machine

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Figure-2.2. Belly Washing Machine.

A top loading machine (shown in figure-2.2) features a hinged top on one side that allows the clothing to be placed inside a watertight tub that is horizontally orientated. This machine is manually operated. This is also called belly machine. The advantages of this machine include ease of operation, user friendliness, and the availability of employees. Top loaders are often cheaper, and can be fit into a smaller place more easily. Some shortcomings include the difficulty controlling all variables, the need to handle manually etc.

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Figure-2.3. Hydro Extractor.

2.5 Hydro Extractor

Hydro extraction (shown in figure-2.3) is an initial step for drying. This method involves partial drying and the removal of surplus water from the garment. A conventional hydro extractor consists of a vertical cylinder with tiny holes in the walls. The centrifugal force responsible for water extraction is provided by a high-speed spin. The usage of a hydro extractor lowers the amount of energy needed to dry any material greatly. This technique removes about 70-80 percent of the water. RPM is a common unit of measurement for speed (rotation per mint). Higher RPM speeds up the process and produces better outcomes in less time. Because the machine runs at a high rpm and carries loads of weight, balancing is crucial in this activity. Load filling is a highly technical and delicate operation that can only be handled by a skilled operator. Improper load filling causes excessive vibrations, which can damage shock absorbers or even break the machine's base 9. Older rotary machines and belly washers, on the other hand, necessitate a separate extraction in a machine developed expressly for that purpose 10.

2.6 Tumble Drying

The next step is to tumble dry the items after the extra water has been removed. Natural gas is used to generate heat in a gas dryer. This heat is applied to the garments when the dryer drum rotates. The dryer drum absorbs heat from the dryer's upper section. In a steam dryer, on the other hand, steam is turned to heat using a heat exchanger. After that, the clothing are heated and dried. Condenser is the name of the heat exchanger that turns steam to heat. Modern dryers, for example, have a design that enables for quick loading and unloading. These machines soften and pre-shrink the garments in addition to drying them 10.

2.7 Pressing

At various phases of the denim washing process, garments might be pressed. Jeans, for example, are frequently pressed to give a flat surface on which to apply whiskers. For a vintage style, press creases or pleats into a garment, or press jeans before curing for a dressier look. Finally, before being shipped to retail, the jeans are also pressed 10.

2.8 Various Types of Washing Method

The presently popular range of forms and styles is just as intriguing as the history of jeans. As a result, for creating special effects, many types of washing processes (shown in figure-2.4) have been employed to provide distressed denim look and have the largest effect on finished clothing 11. The application of dry treatments (e.g. sandblasting, hand sanding, whiskering, tagging, grinding, destroying, potassium permanganate (PP) spray, color spray/sponging, crinkle, laser whisker, 3-D crinkle, PP rubbing, resin spray, heat pressing, pocket marking, center crease, seam marking, crease mark all over, tint, blowout, patch attaching, chevron/knee star etc.) , and wet treatments (e.g., normal wash, pigment wash, caustic soda wash, stone wash, enzyme wash, bleach wash, ice-or snow wash, bio-bleach, net bleach, resin wash, acid wash, milk wash, tie wash) are pretty common in denim garment manufacturing [12, 13].

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Figure-2.4. Various types of washing method

Dry finishing, in particular, has a variety of effects on denim fabric; it encourages people to buy, consequently enhancing its market potential in the denim industry. Denim distressing is both an art and a method. The fashion direction varies across all regions, especially in denim dry finishing, from worn or torn to wrinkled or pressed; these styles can appeal to a wide spectrum of consumers. These can be obtained using a number of denim dry processing procedures, giving the denim fabrics different wash-down looks 14. The denim washing business is working to develop environmentally friendly washing methods that produce no effluent. Because the concept of sustainability is growing, different companies are offering sustainable technologies for denim washing. Dry treatments, or near-waterless treatments, are gradually replacing traditional wet treatments in denim garment washing as a sustainable approach. It's also worth noting that the use of chemical treatments on denim fabric to achieve a fresh look is performing. Biochemical wash has recently become a popular choice among people 15. Starting with one or more wet procedures and ending with dry processes is frequent.

New washing methods for various effects are increasingly being introduced under different terminologies. Moreover, a variety of effects can be generated by mixing different methods. Every step will have an effect on the denim jeans' durability in some way. Expectedly, this process will be really sustainable in the near future. However, as the sewing thread is the most susceptible part of a garment, it must be able to tolerate a wide range of stresses. It is also critical to select the appropriate thread for the washing procedure in order to endure any form of tension.

2.9 Basic Process Flow Chart

Basic flow chart of denim washing is given in figure 2.5.

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Figure-2.5 Basic Flow chart of denim washing 16.

2.10 Machineries of Washing Plant

Different types of machines/tools employed in denim washing process is mentioned below 17:

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2.11 Required Chemicals

Various types of chemicals and their functions in denim washing process are given below 17:

- Acetic Acid

Acetic Acid is employed to neutralize the garments from alkaline condition and to keep the pH level in the wash bath under control.

- Buffer

Buffer is used in the washing plant to adjust the pH of the enzyme, softener, and desizing baths.

- Antistain

Antistain is used to prevent stains on denim weft yarn (white yarn), white pockets of garments, levels, and contacted fabrics of garments, as well as to brighten fabrics. It also functions as an anti-creasing agent.

- Hydrogen Peroxide

In the bleach wash procedure, hydrogen peroxide plays a crucial function. In an alkaline environment, hydrogen peroxide breaks down and produces perhydroxhyl ions, which discolor the coloring ingredients and cause fading.

- Stabilizer

Stabilizer is used to prevent hydrogen peroxide from breaking at high temperatures, allowing peroxide to work smoothly in the bath.

- Sodium Hyposulfite

Sodium hyposulphite is employed to neutralize the garments from chlorine bleach.

- Fixing Agent

Unfixed dye is fixed on fabrics with a fixing agent; when fabric color is properly fixed, color fastness and rubbing fastness are improved.

- Soda ash

Soda ash generates an alkaline environment for pigment dye degradation. Soda ash aids in a consistent bleaching activity in the bleach bath. It has cleansing properties and aids in the fading of textile colors.

- Optical Brightener

The washing plant uses two types of optical brighteners: red brightener and blue brightener. Optical brighteners are mostly used to increase the brightness of apparel.

- Sodium Bicarbonate

Sodium bicarbonate is utilized in denim light shade washing plants in the bleach bath with bleaching powder because it removes color quickly and increases productivity.

- Resin

Resin is a high-efficiency textile resin made from dimethylol glyoxalin monoureine urea that has been etherified. In denim and other cellulose fabrics, resin is used to create semi-permanent creases.

- Potassium Permanganate

For color removal from garments, potassium permanganate is used in acid wash with pumice stone. It is used also spray chamber by nozzle for color out (whitish affect) from the garments.

- Sodium Metabisulphite

The washing plant uses sodium metabisulphite to neutralize the potassium permanganate in the clothing.

- Bleaching Powder (CaOCl2)

Bleaching agent is an oxidizing agent. It's used to get the color out of denim. This substance can be used to achieve various shades (dark, medium, and light) from clothes.

- Desizing Agent

Starches, cmc, waxes, fats, pectins, minerals, and unfixed indigo dye are all removed with a desizing agent from denim, twills, poplin, and canvas fabrics.

- Binder

Binder is a film forming made out of a variety of polymers. During curing, the reactive group in the polymer produces a crosslink.

- Softener (Cationic, nonionic)

It's used to make clothes softer. It has good lubricating characteristics as well.

- Enzyme

During the enzyme wash, the enzyme hydrolyzes the cellulose. It begins by attacking and hydrolyzing the protruding fibers. The yarn section is next attacked and partially hydrolyzed. As a result, color emerges from the yarn part, creating a faded look.

2.12 Flow Chart of Different Types of Washing Methods

Flow charts for different types of washing methods are shown in figure-2.6 to figure-2.14 18:

2.12.1 Normal Washing

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Figure-2.6. Flow Chart of Normal Washing.

2.12.2 Stone Washing

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Figure-2.7. Flow Chart of Stone Washing.

2.12.3 Enzyme Washing

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Figure-2.8. Flow Chart of Enzyme Washing.

2.12.4 Stone Enzyme Wash

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Figure-2.9. Flow Chart of Stone Enzyme Washing.

2.12.5 Silicone Washing

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Figure-2.10. Flow Chart of Silicone Washing.

2.12.6 Caustic Wash

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Figure-2.11. Flow Chart of Caustic Washing.

2.12.7 Bleach Wash

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Figure-2.12. Flow Chart of Bleach Washing.

2.12.8 Acid Wash

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Figure-2.13. Flow Chart of Acid Washing.

2.12.9 Super Whitewash

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Figure-2.14. Flow Chart of Super White Wash.

2.13 References

1. Hoque, Md. Saiful & Abdur Rashid, Muhammad & Chowdhury, Sushmita & Chakraborty, Aishila & Haque, Abu Naser Md. Ahsanul. (2019). Alternative Washing of Cotton Denim Fabrics by Natural Agents. 79-83. 10.11648/j.ajep.20180706.12.
2. Sadeghianmaryan, Ali & Montazer, Majid & Damerchely, Rogheih. (2015). Discoloration of denim garment with color free effluent using montmorillonite based nano clay and enzymes: Nano bio-treatment on denim garment. Journal of Cleaner Production. Vol. 91, Pp. 208-215, https://doi.org/10.1016/j.jclepro.2014.12.014.
3. Halleb, Naima & Sahnoun, Mehdi & Cheikhrouhou, Mourched. (2014). The effect of washing treatments on the sensory properties of denim fabric. Textile Research Journal. Vol. 85(2), Pp. 150-159. https://doi.org/10.1177/0040517514542971
4. Değırmencı Z. Study on the Loss of Strength of Denim-like Knitted Fabrics after Different Washing Treatments. FIBRES & TEXTILES in Eastern Europe 2017; 25, 3(123): 98-105. DOI: 10.5604/01.3001.0010.1697
5. Uddin, Mohammad. (2014). Indigo ring dyeing of cotton warp yarns for denim fabric. Chemical and Materials Engineering. 2. 149-154. 10.13189/cme.2014.020701.
6. Retrieved from https://www.scribd.com/document/421834633/Tonello-Tusuka-Washing-Ltd-pdf
7. https://en.wikipedia.org/wiki/Washing_machine
8. Ahamed, J. , Mahmud, M. , Ahammed, M. , Mia, R. , Hasan, M. , Khan, T. , Limon, G. and Shamim, A. (2021) Evaluate the Strength of Denim Goods Using Different Washing Technique. Journal of Materials Science and Chemical Engineering, 9, 1-8. doi: 10.4236/msce.2021.93001.
9. Abdullah, Traditional Hydro Extractor, July, 2010. Retrieved From http://www.denimhelp.com/traditional-hydro-extractor/
10. Denim Finishing Machinery, https://www.cottonworks.com/topics/sourcing-manufacturing/denim/finishing-machinery/
11. Khan, Md & Mondal, Md. (2012). Bleach Washing Combined with Pumice Stone for the Modification of Denim Garments. Oriental Journal Of Chemistry. 28. 1241-1247. 10.13005/ojc/280320.
12. Shamsuzzaman, M., Kashem, M., Sayem, A. M., Khan, A., Shamsuddin, S., & Islam, M. (2021), Quantifying environmental sustainability of denim garments washing factories through effluent analysis: A case study in Bangladesh, Journal of Cleaner Production, Volume 290, https://doi.org/10.1016/j.jclepro.2020.125740.
13. Mohibullah, ATM, Takebira, U.M., Rahman, M., Alam, M.S., Sarker, A.S.M.S. and Mahir, S.Q. (2019) Costing Principles of a Denim Pant. Journal of Textile Science and Technology, 5, 48-60. https://doi.org/10.4236/jtst.2019.52005
14. Aravin Prince Periyasamy, Govardhana Rao Chilukoti, and K Thavasiappan, Dry finishing: Enhancing value of denim, Feb 2012, Indian Textile Journal. Retrieved from https://indiantextilejournal.com/articles/FAdetails.asp?id=4330
15. Mst. Murshida Khatun, Upama Nasrin Haq. Effects of Biochemical Wash on 100% Cotton Denim Apparel. American Journal of Chemical Engineering. Special Issue: Advanced Chemical and Biochemical Technology for Biofuels. Vol. 5, No. 2-1, 2017, pp. 6-14. doi: 10.11648/j.ajche.s.2017050201.12
16. Retrieved from https://aaa-control.info/portfolio/denim-washing-and-finishing-techniques/
17. Retrived from https://garmentsmerchandising.com/types-of-machine-used-in-garments-washing-plant/
18. Hossain M, Shakhawat Md, Hossain R, Shakhawat Md, Hasan K, Hossain Md, Zhou Y. Effective mechanical and chemical washing process in garment industries. American Journal of Applied Physics. 2017; 2(1): 1-25.

3 Terminologies of Denim Washing

Compiling terminologies, indeed, is not a scholarly work; however, it is required to know the different types of terminologies, providing a reader new to this process a chance to become familiar with the specialist terms. From that perspective, hereby, it has been attempted to compile necessary terminologies related to denim washing. Even though details are not targeted, for basic comprehensions, some of the terminologies are presented little bit longer in this chapter.

1. Raw Denim ( Dry Denim)

Raw denim refers to denim that has not been washed or treated. The product is a robust, durable fabric made of 100 percent cotton and left unmodified after the dyeing and finishing process. There are two types of raw denim: sanforized and unsanforized.

2. Pre-washing (Washing)

Pre-washing, commonly known as washing, refers to the industrial operations that use water, chemicals, and abrasive techniques to give denim clothes a worn appearance or increased softness.

3. Shrink-to-Fit

Shrink-to-Fit denim is raw, unsanforized denim, meaning that no shrinking was applied during the manufacturing process. Before methods such as sanforization and stonewashing were available, people were compelled to purchase their jeans a couple of sizes larger. Such un-treated jeans were soaked before being worn to shrink and soften the stiff fabric of the jeans. People who buy loomstate denim can experience the "Shrink-to-Fit" effect 1.

4. Sanforization

On the first wash, raw denim can shrink up to 20%. Sanforization is a process that stretches and pre-shrinks cloth before it is cut or washed, reducing shrinkage to less than 3% 2.

5. One-wash

One-wash denim is unsanforized denim, which is sometimes confused with sanforized denim. Technically, "One-wash" jeans have been washed once in an industrial washing machine to remove the majority of the shrinkage from the fabric, resulting in softer, ready-to-wear denim.

6. Desizing

Desizing is a method of softening denim by rinsing it. The amylase enzyme targets the starch and removes it from the fabric during the de-sizing process. Although this technique marginally diminishes color, it is generally employed to enhance denim softness and drapeability 3.

7. Fade(s)

It is mainly lighter areas present in denim after repeated wash and wear. When dyes are stripped out of the warp yarn or the core fibers are damaged and exposed, fades occur. Fades appear in the stress areas and hinges of jeans, particularly around the knee, hip, hem, and thigh, as familiar patterns with names like whiskers and honeycombs. Although abrasion techniques such as sanding and shaving, as well as stone and enzyme washes, can be used to artificially produce fades, most denim fans prefer to earn their fades over time 4.

8. Rinse Wash

Rinse' is a term that implies 'flush' or 'wash thoroughly.' This is a straightforward washing procedure that uses slight detergent and back stainer. The jeans' original color is nearly unchanged, and the fabric has been given a slightly different but natural dry to grainy texture. This method of washing also prevents future shrinkage. This finishing process, on the other hand, has no effect on the sewing thread 5.

9. Silicone Wash

In textile washing, silicon wash is an essential and common step. It is also a widely used washing method. Silicone wash can be used on a variety of fabrics, including knits, corduroy, denim, canvas, and twill. This wash offers clothing an elastic feel and long-lasting softness. It improves fabric tear resistance, anti-pilling properties, and dimensional stability. It also makes cutting and sewing fabrics easier. Denims are made soft and easy to wear thanks to the introduction of granular silicone softening technology, which uses fewer resources and even combines a few procedures, reducing water use by around 50 litres per pair.

10. Normal Wash

Typically, a normal wash consists of a rinse wash and a softener wash. In this situation, the rinse wash is completed first, followed by the softener washing. Normal wash eliminates several types of dust, dirt and starch from the surface of the denim 6.

11. Stone Wash

Stone wash is a traditional washing method in which abradants such as volcanic rocks or pumice stone are added to the clothes while they are being washed. Stone washed items have an aged appearance and are often puckered at the seams. Stonewashing is usually done on textiles that have been dyed with indigo and are prone to losing color due to abrasion. Ring dyed yarns are frequently utilized, which indicates that only the surface fibers have been dyed, leaving the center uncolored. Natural and artificial stones are used in stone washing. The use of ordinary pumice stones can result in a variety of issues, the most common of which are difficulty in removing lingering pumice from treated garments, physical harm to garments and machines as a result of an excessive load of pumice pebbles, and congestion in the machine drainage system lines. Artificial stones can be manufactured of coal or ceramic and can be adjusted to provide the desired look. Stone washing damages fibers to varying degrees, depending on the type of stone employed and the length of time the garment is stone washed [7, 8].

12. Super Stone Wash

Over six hours of stonewashing is applied to the garment. For hard washing, soda ash and soap are used. To complete the process, steam is utilized at 600-800C for an hour, followed by an acetic acid wash. After that, the garment is neutralized and rinsed 9.

13. Bleach Wash

With or without the addition of stone, an oxidative bleaching agent, such as sodium hypochlorite or potassium permanganate, is used to achieve the bleaching effect. Bleaching chemicals effectively remove the dark blue colour by destroying the indigo dye molecules. To reduce yellowing and tenderness, bleached fabrics should be antichlored or washed with peroxide. The bleaching strength, liquor ratio, and treatment time all influence the final color. For medium to vintage denim effects, sodium- and calcium hypochlorite are typically utilized, whereas potassium permanganate is used for ultra-vintage and light shade looks. When a light bleach effect is desired, or if the fabric is sulphur colored, hydrogen peroxide can be employed. Bleaching can harm fibers, and controlling reactivity during the bleaching wash is difficult. Materials should be properly sorted before manufacture to ensure color consistency [7, 10].

14. Acid Wash (Moon Wash)

Acid wash on denim jeans is becoming increasingly fashionable as a result of its striking contrasts and vibrant colors. Fabric clothing with an indigo and sulphur base can be acid washed. It removes the top layer of color from the cloth, making it whiter and imparting it a faded appearance. This wash is done by immersing the stones in bleach and then neutralizing the acid. Tumbling the clothing with pumice stones presoaked in a solution containing sodium hypochlorite (5-10%) or potassium permanganate is a common method (3-6%). Localized bleaching occurs, resulting in a non-uniform bright blue/white contrast. Water is not used in this wash. Optical brightening treatment can improve the color contrast. Acid washes are popular, particularly for summer denims. In 1986, the technique was invented in Italy and patented. Cotton balls or cotton ribbons are utilized instead of pumic stone in some variations of this procedure. Cotton has a significantly different effect than pumic stone. It has a more merged and cloudy appearance 9.

15. Acid Stonewash

Acid stonewashing is typically done on heavy fabrics like denim, canvas, and twill. During acid washing, pumice stones are employed 11.

16. Snow Washing

Snow-washed denim is a more extreme version of acid-washed denim, in which the denim has been acid-washed until the denim displays vivid white highlights 1. This is performed by dry tumbling denim with pumice stones soaked in bleaching agents to create a'snow' pattern. To remove the color from garments, stones are used to deposit a chemical on clothes. This chemical coating only removes color from the garments' outside surface, giving them a frosted appearance. The most common possibilities for this process are indigo and certain sulphur dyes.

17. Towel Wash

Towel Wash is a method for developing cloudy, marble, or random effects on denim garments by combining Japanese bleach or potassium permanganate with a towel. This is an uneven wash technique in which not all clothing have the same impact but the overall theme is the same. Denim is towel washed for a rich or attractive look. It belongs to the acid wash family. Potassium permanganate is always used in this method, but Japanese bleach is occasionally used as well.

18. Thermopol Wash

Thermopols are used to wash knit, soft, and light clothes. The clothing have a lengthwise fading effect. Thermopols are foams with a cubic structure cut into 1 inch or 0.5 inch cubes. Typically, 5-10kg thermopols are fed into the belly machine, and the solution is distributed out through those little thermopols, and the machine is run for 2-3 minutes to mix the solution. The garments are then fed into the machine for dry tumbling once they have been combined. Because KMnO4 or NaOCl are hazardous compounds, they must be neutralized before proceeding. It's a subtype of acid wash 12.

19. Rubber Ball Wash

Rubber ball wash is a garment wash effect that can be chosen during the production process. To obtain a softer hand feel and more seam abrasion, specially sized rubber balls are put to the garment softening bath or during the drying treatment 13. Different types of acid wash effects are depicted in Figure 3.1.

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Figure-3.1 Various types of acid wash effects 14 [Image Courtesy: https://textilestudycenter.com/acid-wash-random-wash/ ]

20. Mill Wash

Denim fabric that has previously been washed and supplied to cutters or garment manufacturers is referred to as mill wash 3.

21. Enzyme wash (Bio-Stoning)

Enzyme washing (Bio-Stoning) is a method of removing exposed cellulose from denim by using enzymes. This method loosens dye particles and aids in the creation of a faded or worn appearance. Because of its non-toxic and environmentally beneficial properties, enzyme wash in the textile industry is one of the most quickly increasing topics in industrial enzymology. Process economics, fashion, and, to a lesser extent, environmental impact have all influenced the denim finishing industry's shift to biostoning. The same hand may be created with enzyme washing as with stone washing, but this technique is more kind on the fibers on a microscopic level. Amylase, Cellulase, Laccase, and Catalase are the four types of enzymes used in washing. Cellulase enzymes are a group of enzymes that break down cellulose into glucose and other low-molecular compounds. Cellulase enzymes hydrolyze cellulose fibres on the surface, removing all surface fibres, including those that hold dye. Furthermore, enzyme is sometimes added to enhance the stone's effect. The neutral enzymes cause less back staining and operate best when the pH is between 6.0 and 8.0. They also perform best at 55° C. Acid cellulose enzymes work best when the pH is between 4,5 and 5, and their activity is at its peak at 50° C. Because of the enzymes' sensitivity to temperature, time, and pH, the process must be carefully regulated. These three variables have a significant impact on the outcome, and large variations can harm the fabric. Damage to the strength of the fibers and highlights on the seam can be avoided under strict control. To ensure that no enzyme residue remains after an enzyme wash, a washing step that rinses the clothing must be completed. Backstaining is one of the issues that can arise during the denim biostoning process. For consumers, this detracts from the garment's appearance 7.

22. Super White Washing

Super white washing is a common wash (bleaching wash) approach for brightening the appearance of denim items. The garment appears incredibly white after applying the super white wash. The whitening agent is sometimes employed. The garments made of cotton grey fabric are given a super white wash. Optical brightening or whitening agent is the most commonly utilized chemical in this washing.

23. Bio polishing

Cotton and other natural and artificial cellulosic fibers can benefit from an enzymatic treatment termed "biopolishing" in addition to the "biostoning" method. The main benefit of this method is that it prevents pilling, which causes an unappealing, knotty fabric appearance, lowering garment quality. Because microfibrils (fuzz) projecting from the surface of yarn are the most sensitive to enzymatic attack, cellulases hydrolyze them. The microfibrils become weaker as a result, and they break away from the main body of the fiber, leaving a smoother yarn surface 15.

24. Heavy Stone Wash

Stone washing and enzyme washing are combined in a heavy stone wash. The advantage of heavy stone washing is that it takes less time to process and uses approximately half as many stones and enzymes. The abrading effect of heavy stone wash varies depending on the stone type, enzyme type, and process duration 7.

25. River Washing

River washing is a method of giving denim a vintage, worn look by combining pumice stones with cellulase enzymes. For the first cycle, the washer is merely loaded with stones and fabric. For the second stage, enzymes are combined with the stones and tumbled until a genuinely aged appearance is achieved 3.

26. Tie Wash

Tie & Wash, also known as crunch wash, creaking pattern, or marbling effect, is a common feature in high-end clothing. The fabric of the garment is knotted after folding and then washed in this effect. When net pockets/bags are used instead of tying, it creates a similar effect. The entire garment is encased in a net bag. The fabric in the folded portions was less washed after washing than the edges generated by folding, and the original colors had a comparably high intensity 17.

27. Soft Wash

In this washing process, so-called softeners are employed to make the fabric feel softer while leaving the color almost unaltered.

28. Pigment Wash

Pigment washing is the simplest of the all-wet wash techniques, but it is also the most expensive. It produces a light wash effect that resembles fresh color clothes. It's done to give the seam area a fading/old-looking aspect, as well.

29. Caustic Wash

Caustic wash is a relatively recent process that is gaining ground in the clothing industry. Caustic wash is one of several distinct types of washes available, depending on market demand and the fashion clothing sector. Pre-printing wash is another name for caustic wash. To eliminate contaminants, reactive dyed, sulfur dyed, direct dyed, and printed clothes are frequently washed with caustic 6.

30. Enzyme Bleach Wash

In the case of enzyme bleaching, the enzyme wash is completed first, followed by the bleaching procedure using chlorine or non-chlorine bleach. Because the enzyme bleach wash shade ranges from dark to light, more caution is required 6.

31. Ultrasonic Washing

Using high-intensity sound waves in a fluid medium, ultrasonic washing generates mechanical forces. Because of the ultrasound's action on the cloth, the liquor absorbed by it compresses and expands on a regular basis. As a result of the fluctuating pressure, microscopically small cavities appear in the liquid. Intense shock waves are generated when minute cavitation bubbles smash on the solid substrate's surface, causing effective stirring and mixing of the modified liquid layer. Ultrasonic energy creates millions of bubbles or cavities in a liquid at a very high frequency, which strike the target material surface constantly and remove unwanted substances from the fibers. The power of ultrasonic cavitations in liquids is one of the most important parameters for the ultrasound mechanism. When compared to traditional washing methods, ultrasonic washing has many advantages, including greater cleaning qualities, reduced process time, energy, and chemical use, and less fiber migration due to ultrasonic agitation. Other washing methods used in an ultrasonic environment boost the efficiency of the worn-out process while reducing back-staining [18-20].

32. Petroleum Wash

Petroleum wash is a denim treatment devised in 1992 by the U.S. brand Willi Wear. Left-hand denim is enzyme-washed until it has lost majority of its color. It is then over dyed and placed through a silicone wash, which gives it an oily covering, and, in turn, a super-soft, butter-like hand 3.

33. Hyper Washed

A word used to describe fabric that has been regularly washed to create an ultra faded effect 2.

34. Overdyeing and Tinting

After the stonewashing process, denim garments are frequently tinted. The garment has been lightly colored to give it a small change in the final denim appearance. Tinting is a dyeing procedure that uses a small amount of dye and primarily direct dye. This is being done to affect the indigo's colour, cast, and tone. To give garments a worn and muddy appearance, tinting is employed. 'Dirty Denim' is frequently achieved by dying denim with a yellow over dye. One can make select regions look dirtier than the surrounding areas by localizing the tint application. Tinting is normally performed with either direct dye or reactive dye. After basic washing, some tint is introduced to the dye bath before the softening process to make it somewhat bluer, yellower, greener, redder, or any other shade to match the wash target; this occurrence is known as tinting. This is not real overdyeing; rather, it creates the illusion of a change in the fabric's general color. Denim overdyeing/tinting is a type of dyeing that is applied to jeans after they have been made to give them a different tone of color. This dyeing is done over either dyed or white clothing, hence the name "over dyeing." This method uses a significant amount of water and chemicals.

35. Cast

Casting is a denim dyeing technique that results in layered-color jeans. The two most popular casts for jeans are greencast and redcast. Greencast jeans are colored with green sulfur and indigo, and after several washes, they acquire on a light blue colour. Before washing, Redcast jeans are dyed solely with indigo, giving them a nearly purple appearance; after several washes, the denim fades to a brilliant blue 13.

36. Random Wash

Random wash is another name for acid wash. The effects of fading are irregular and uneven. To get the required random effects on the garments, a certain amount of treated stones and garments are dried tumbled in the belly washing machine.

37. Hydrose wash

Hydrose wash, a new concept researched by Rashid et al., of denim garment washing, which uses varying concentrations of hydrose on denim fabric in an alkaline environment. Denim fabrics are dyed with vat dye (i.e., indigo dye), which is insoluble in the fiber until it is treated with hydrose and NaOH to make it soluble. Dye molecules can be easily detached from fiber without causing damage to the fabric 21.

38. Tacking (Tagging)

Tagging or tacking refers to the process of tagging or tacking garments that have not been washed. Tag pins are used to secure the fold in specific parts of the garment. Now the garment is processed in washer and a permanent fold appears after removal of tag pin. Because it is less exposed to mechanical rubbing and chemicals, the inside of the fold has a darker tone. Variation is provided by using different lengths of tag pins varying from 05 mm to 15 mm. In industry, this length range is more typically employed. Tacking is most commonly done on the waistband, bottom hems, back pocket, and front pocket corners, among other places. Tacking can be used to create horizontal or vertical patterns on the front or back of a garment 22.

39. Stained Jeans

Denim is sometimes stained with different pigment colors, dyes, or even dark oils to give it a vintage look. On an indigo background, this is a really artistic touch that is designed to look stains gorgeous. It's generally put to distressed and torn-out jeans to give them a more vintage look. It's also well-known when worn with light-colored denim or an acid-washed background. Pigment solutions are brushed onto needed locations to create dark brown stains with a muddy appearance or green pigment to simulate grass stains. Painters' jeans are sometimes made with malty colors. Spray guns can also generate stains. Spraying several dye colors on jeans while maintaining the gun at a low air pressure creates a lovely and natural pattern. Color dropping stains are also made using the dip and drop technique. It's used on baby girls' denim to give them a bright appearance 22.

40. Sun Washing

Bleaching and toning can provide a little shade that looks as if the jeans have been sun faded.

41. Bio rubber

Rubber stone designed for stone-wash treatment. It performs well when used in combination with enzymes.

42. Antichloring

Antichloring treatment is required as traces of NaOCl is left on the fabric that forms hypochlorous acid. This may yellow and weaken the fabric.

43. Neutralization

Potassium permanganate (PP) and acid washes are acid-based. So, they need to be properly neutralized to bring jeans back to a neutral PH otherwise the garments will irritate consumers’ skin. P.P chemical has to neutral by using sodium metabisulfite.

44. Hydro-extracting

After finished the washing process, all denim garments are unloaded from the washing machine to a trolly and keep this to the hydro extractor machine for removing the extra water.

45. Washing Effluent

Effluents released by denim garment washing factories is called washing effluent.

46. Back-staining

Back staining is a significant issue in the denim washing industry. Back staining (figure 3.2) is the re-deposition of discharged indigo from the process bath onto the fabric. As a result, the weft thread and the white pocket lining have a bluish tone that is well dispersed. Desizing, stone washing, or enzyme stone washing are the most common causes of back staining. Back staining is generally defined as developing a good contrast between the blue and white yarns. The difference between the blueness of the blue yarns and the whiteness of the white yarns creates the contrast. The re-deposition of indigo on white denim can be used to measure back staining [23, 24].

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Figure-3.2 Back staining of Denim Garments.

47. Anti-back Staining Agent

Anti-back staining agents are used in the wash bath to prevent back staining. These agents, along with other chemicals associated with the respective washes, are added to the bath. These compounds are capable of preventing the re-deposition of dyes that have been removed from the garment. Most anti-back staining chemicals are highly effective in soft water, however they may be less successful in hard water, causing the dyes to re-deposit. This is because hard water includes salts known as electrolytes (exhausting agents), which assist indigo colours in soiling more quickly. Anti-back staining agents now include sequestering agents, allowing them to be utilized in hard water. Anti-back staining agents include enzymes such as cutinase enzymase and other lipolytic enzymes. All of these methods effectively decrease back stains, but they are also more expensive. Using oxidizing chemicals is another technique to avoid back staining. Oxidizing chemicals operate on glucose to reduce its reducing power, resulting in no back staining. Bleaching agents include hypo chlorites, permanganates, and peroxides, among others. Resist Salts, which are mild oxidizing agents, are also available 24.

48. Sand Blasting

Sandblasting is the method of scrubbing a garment with high-pressure air mixed with very tiny sand particles. When the garment's surface area is blasted, the effect is nearly identical to that of worn-out jeans. Sand blasting produces a very consistent outcome that is unachievable with its alternatives. Its specialty is the merging effect that is blended with such a beauty that it has no difference with natural effect. Front thigh, back seat, back panel near bottom, or front panel around knee are all areas that can be sandblasted. Full body blasting is sometimes used to give cloth a unique look. Intense blasting may be used to develop hot spots for a more realistic look on the front knees or back seat. Sand blasting is often employed by denim garment manufacturers in two ways: Mechanical and manual. Sand is mixed with pressurized air in a chamber and sprayed on the garment to rub out the color of the cloth from the sprayed area in the mechanical process. The chamber's purpose is to restrict sprayed sand from spreading and harming the environment. On the other hand, in the manual method, sand paper is used to create the effect. The sand paper is attached to a wooden block that is rubbed against the garment's surface. This is a time-consuming operation that requires two people to complete on a single garment. This department is typically hired on a contract basis and paid on a piece-rate basis.

49. Silicosis

Silicosis is a fibrotic lung illness caused by inhaling crystalline silicon dioxide or silica. It is one of the most common occupational diseases in the world. Sandblasters who work with denim are at a significant risk of developing silicosis. Patients who develop silicosis as a result of denim sandblasting have a rapid disease development, and many of the silicosis consequences, including mortality, appear to be unavoidable 26.

50. Local tint staining effects / bleached spots

Diluted solutions of oxidizing agents are sprayed on or applied with a sponge after the wet process neutralizing 25.

51. Naturally Aged Raw Denim

Denim is one of the rare items that look better with age. The effect of natural wear-in occurs slowly over time, and frequent use gives an aged appearance.

52. Faded Denim

Faded denim refers to denim that has been washed back, treated or naturally worn until the denim fades from its original darker state 2.

53. Destroying ( Destroy Wash)

In the fashion industry, destroy wash has become the most prevalent and popular. Dry washing is commonly done in a grinding machine with various sized stones. The weft yarn becomes significantly worn down as a result of this process, making the garment more appealing and trendy. The clothing are destroyed using various devices such as a grinding machine, a hacksaw blade, a needle, a knife, and so on 6.

54. Atari

Atari is used to describe all fading that occurs on frequently rubbed or creased parts of raw denim jeans.

55. Abrasion

Abrasions relate to a denim pair's 'worn in' or distressed portion, when the cloth appears to be highly worn. During the production process, abrasions are formed using pumice stones or applied with equipment like sanders 2.

56. Whiskers (Wear Marks)

Whiskers, also known as Mustaches, Hige (pronounced "Hee-gay"), Crease Lines, and other names, are a fading pattern on the front rise characterized by horizontal or slightly angled lines (shown in figure 3.3) that start at the fly and can stretch across the pockets to the outseam. Denim is folded and stretched while seated, resulting in this common pattern. Slimmer fits crease more cleanly with less fabric, resulting in tight, straight lines. Larger, drooping whiskers are more common in looser, standard fit jeans. Depending on the fit, whiskers may appear on either side of the knee. It's also a physical procedure that produces the look of aged denim by fading the ridges in the crotch and back of the knees. It can also be dark wrinkled in faded denim in the other direction. Industrial fading procedures like as lasering or sandblasting can also be used to create them [1,3,27].

57. Whisker Texture

Next to the whiskers, valleys or dark regions develop. This occurs where the denim has stretched and pulled as a result of movement 27.

58. Hand sanding

Hand sanding is a method for obtaining whiskers (the feline wrinkles on the upper thigh) and other destruction patterns that would otherwise be developed by wear 28.

59. Chevrons

Stretch marks on the inner thighs are known as chevrons. They're normally more intense around the crotch area and fade out closer to the knees 29.

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Figure-3.3 Differences of various fading effects between naturally aged (left portion) and washed denim (right portion) 29.

60. Hot Spots

Hot spots are a heavy/intense area on the thigh or knee that is formed intentionally to create a used-look, and if there are any whiskers lines on the knee area, it is referred to as a knee star 30.

61. Scrapping

Partially worn out with a grinding stone, used on pockets, belts, and the reverse side of the legs.

62. Pocket Mark

Scraping is done to make the inside pocket visible .

63. Crotch Fading/ Blowout

A crotch blowout (shown in figure 3.4) is a rip, tear or hole in the crotch area of your jeans, due to the amount of friction and tension that the fabric endures. Wrong care accelerates the aging process. If users don't wash their jeans often enough, dirt and bacteria will build up, loosening the fabric and making them more prone to crotch blowout 31.

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Figure-3.4 Crotch fading/ Blowout 32.

64. Center Crease

It is a dry process which produces crease mark in the middle side of front and back part of denim jeans. Putting pattern at inside of denim pants is required before using abrasive paper to get this effect. After washing, this effect will be visible.

65. Roping Effect /Hem Fading

A repeating fade pattern that develops along the hem at the end of each leg, particularly after washing. It is the sought-after result of what is technically an error in vintage chain stitch sewing machines 33. Old Levi’s XX pairs are known for their strong roping 1.

66. Honey Comb Fading (Comb Marks)

Honeycomb fading is a type of fading that occurs behind the knees and is formed like honey combs (shown in figure 3.5). Honeycombs look brighter on tighter fits, while wider fades emerge on looser fits 27.

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Figure-3.5 Honey comb fading 34.

[Image Courtesy: https://www.denim-fever.net/denim/honeycombs-on-jeans/]

67. Fly Abrasion

The fly abrasion is an extension of the whiskers. Depending on whether the jeans have a button or zipper fly, fly abrasion can take several shapes. It also depends on how loose or tight the jeans are fitted. When whiskers appear over the fly, it is being influenced by hip stress, which is most common in button flies 29.

68. Thigh Fading

Fading on the thighs happens from abrasion in this area. When sitting, we rest our arms and hands on our thighs, rubbing off color 27.

69. Knee Fading

The knees are one of the most stressed areas on jeans. If you do a lot of bending and work on your knees, this area will fade significantly 27.

70. Waistband Fading

Fading on the Waistband is most often caused by friction from wearing a belt. Random exposure of the seam line inside the waist band becomes evident 27.

71. Rear Knee Lines

Rear Knee Lines are the honeycomb like texture that forms at the rear side of the knees from walking and the sitting position 29.

72. Knee Stretch Marks

Stretch marks created by the stress of bending the knees. These marks usually extend over the outer seams and fade into the wrinkles at the rear side of the knees 29.

73. Belt Loop Fading

Like other raised areas, the belt loops end up taking a lot of wear from abrasion. They end up brighter than other points on the jean 27.

74. Wallet Fading

Wallet fading refers to the faded outline of a wallet on the back pocket. The fatter the wallet and the tighter the fit of jeans, the more worn the outline becomes. Wallet fades can be the first or last fade patterns to develop but are easily one of the coolest.

75. Tate-Ochi

A Japanese term that translates directly as ‘vertical falls’, referring to vertical faded stripes in (vintage) denim made from slub yarn. The unevenness of the thread causes the thicker parts to fade more rapid 1.

76. Iron Fading

It's a technique that involves pressing a hot iron against the surface of denim garments to achieve a certain effect.

77. Tear Effect

The garment is given torn effect after washing. The clothing is washed after two horizontal cuts. Threads come out of the garment after washing. To get this effect, vertical threads are eliminated from the garment, leaving only horizontal threads 17.

78. Fraying Wash

Fraying wash, in other words, is the disintegration of denim fibers in certain places of the jeans, such as the waistbands, pockets, and hem 9.

79. Scrubbed

The surfaces of the denim trousers are scrubbed with brushes in this process, to effect suede and partially fluffy appearance 35.

80. Patch and Repair

Manual processes used to obtain a vintage look and unique and individual effects. The look is achieved by tearing the cloth in a specific region and then manually or with a sewing machine putting it back together. The obtained effect (shown in figure-3.6) is new or used vintage 25.

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Figure-3.6 Jeans with patch effect 25.

81. Mannequins

The word mannequin (shown in figure-3.7) is derived from a Dutch word 'manneken' which means 'small man'. It is a model of human body used during manual brushing of denim garments.

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Figure-3.7 A horizontal mannequin 36. [Image Courtesy: https://www.tonello.com/en/product/scratch-o]

82. Grinding Effect

Grinding is being done on pocket edges & bottom hems edges (shown in figure-3.8) by running against abrasion surface or stone to achieve worn-out effect. Many different makes of machines & pen grinding tools are available in the market, which run on pneumatic system 30.

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Figure-3.8 Grinding effects in pockets 37.

83. Dremel tool

A dremel tool (shown in figure-3.9) is a handy multi tool that happens to be perfect for distressing denim. In fact, this is one of the factory-methods to create distressed jeans.

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Figure-3.9. Dremel tool.

84. Resins

Resins are viscous liquids with the ability to permanently harden. Resins mainly fall into two groups; one is deposition type of resins. This type of resins is deposited on the fabric as surface coating. Between the fiber and the resin, there will be no reaction. They include Phenol-formaldehyde resins, Urea formaldehyde resin, Alkyd resins, Ketone resins, Vinyl resins etc. Another is Cross linking type of resins. These types of resins chemically react with the fiber and cross link the fiber molecules 38.

85. Crinkle/Wrinkle

A wrinkle, often referred to as a rhytide, is a fold, ridge, or crease in fabric or clothing. It is the fabric deformations based on its viscoelastic properties, meaning a slight depression in the smoothness of a surface. Fabric with wrinkles has a vintage and aged appearance. By manipulating denim clothing in various ways, wrinkles on overall clothes or specific desired locations can be made manually or automatically 38.

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Figure-3.10. 3D Crinkle Effect 38.

86. Resin Application (3D Effect)

Denim jeans are generally dipped or coated with resin to stiffen them 39. To achieve a 3-D effect (shown in figure-3.10), after applying the resin solution in the proper proportions, manual designing is done as needed on the thigh, hip, and back knee area. After that, it must be manually dried with a hot press or a hair dryer, and then cured in an oven at the proper temperature and time as specified in the resin product manual. The 3-D effect will not be permanent if the resin is not properly cured, and the wearer may experience skin discomfort or rashes. This process must be carried out by highly skilled operators in order to achieve consistency and uniformity. By dipping the garment in resin and crushing it manually, then curing it in the oven, the entire garment can have a crushed look. Silicon is crucial for obtaining softer hands after being in the oven 30.

87. Curing

Curing is a thermal operation that causes the garment to become harder, tougher, and more durable. It takes place usually in a steam atmosphere or in a dry heat environment. Temperature and cycle management are the two most crucial variables for high-quality 3D crunching / wrinkling. To achieve the proper temperature (145–160°C) and time (7–22 minutes), oven curing is recommended. Some common industrial ovens are used extensively, such as automatic type ovens with conveyors, box type curing ovens with trolleys, and semi-professional curing ovens with conveyors 38.

88. Permanent Crinkle (Baked Effects)

Denim is treated with resin to keep the crinkles effect even after washing. The crinkles become permanent as a result of the heat.

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Figure-3.11. Double Head Crinkle Machine

89. Double Head Crinkle Machine

The Double Head Crinkle Machine (shown in figure-3.11) is used to create permanent crinkle effects on a variety of garment sections. It is generally preferred due to its ease of use. It is simple to create crinkle effects on desired portions of clothing with the machine's double creasing frame, regardless of garment size.

90. Octopus Crinkle Machines

This machine includes a double header, six heads, and six legs, each with its own heating system. Six locations can run at the same time. The entire system can be controlled by two users. The machine creates a realistic 3D effect. Each of the six legs and heads can be controlled independently. It is possible to make a front pocket with regions and subsequent fractures at the same time.

91. Over All Wrinkles

After washing with resin and hydro-extacting, the whole garments are dried, and a distinctive look is obtained. The garment is tied with thread, net, or rope that has been treated with resin for the effect. Crinkle is applied to a variety of materials, including denim, twill, canvas, poplin, knit, viscose, and nylon. This is completed after all types of dry and wet processes have been completed. This is currently quite popular and commonly utilized in denims.

92. Plated

Plated is a form of finishing that gives a stonewashed appearance to Jeans wear using natural earth pigments. It looks real, but it’s a trompe l’oeil 3.

93. Quick wash denim

A customized dyeing procedure is used to dye the quick wash denim fabric. So that indigo color may be removed fast during the wash cycle. Giving washed look at shorter washing cycle. This results in more cost-effective washing, with less water used, fewer chemicals used, less time spent, and fabric strength maintained 40.

94. Coating

The technique of adding a pigment, acrylic, or polyurethane to a garment in the last phases of production to avoid fading or staining is known as coating. Pigment coating gives a 'leather' or 'wet' appearance, whilst acrylic and polyurethane are transparent 2.

95. Ozone (O3 )

Ozone is a gas that is naturally generated by photochemical reactions with sun UV light and is found in our atmosphere. It can be created artificially in a variety of ways, including corona discharge. Three oxygen atoms make up ozone, which is a triatomic molecule. Ozone has a great propensity for reacting with practically any organic material. Ozone is a strong oxidant and disinfectant that can destroy viruses, parasites, and bacteria's biological structure. It offers some advantages over other oxidants typically employed in the textile sector, especially when it comes to chlorine. The bleaching method in the denim industry uses ozone (O3). The key benefit is that ozone is chemically unstable and does not leave any secondary derivative products on treated goods 41.

96. Laser Wash

Lasering is an alternative to sanding, brushing, and the use of chemicals. Whether lightening the surface or partial brightening or engraving logos and patterns into the fabric: the laser beam can deliberately fade the dye, slightly scratch or even destroy the top fabric layer, creating holes or cracks. Synthetic fibres such as PES, polyamide, and lycra, on the other hand, might melt and leave hard residues. As a result, lasering is restricted to cotton outer materials, but the material composition of the sewing thread must also be considered. Although laser technology has the advantage of precise fabric surface treatment, it is generally more expensive than other approaches 5.

97. Laser Marking

In the laser marking process, the laser works on a surface layer. This method replaces the phases of dry or water-based discolouration, giving the garment a distressed impression.

97. Laser Spray Painting

Different patterns or motifs, such as photographs, images, lines, or text, can be drawn on denim garments using a computer-controlled process. Chemicals or pigments are sprayed onto the cloth to create various patterns, which are then cured. Advantages include no use of water, zero effluent discharge, negligible chances of human error, excellent reproducibility and higher productivity, less maintenance and cleaning of machines, less time consumption and no adverse effect on fabric strength 9.

98. Laser Engraving

The laser engraving process works more in depth. It modifies the fiber of the fabric. For this reason, the obtained result is also tactile. Laser engraving can be done on a specific area of the finished garment or all of it.

99. NEP (Never Ending Laser Power)

The component that produces the laser beam is referred to as a laser tube. This laser tube is made out of a sealed chamber with high-tech components and a CO2 gas mixture. When the laser beam is produced in the laser tube, the chemical structure of the gas mixture in the sealed chamber slowly changes. The reduction of laser output power over time is caused by changes in the chemical structure of gas. The CO2 gas mix in VAV Technology's Never Ending Power Laser Tube is regularly regenerated and never loses its quality, thanks to the use of changeable gas mix cartridges that ensure a consistent quality and amount of gas in the sealed chamber 42.

100. Laser Whisker

This whisker is done by laser machine. Here, garments specific areas are burned by imposing laser with high intensity. After wash, the burned indigo color will be removed and whisker effect is obtained.

101. The Laser Conveyor

Machine for continuous processing on conveyor belt or a traditional fixed table. It allows non-stop laser processing and garment unloading 43

102. Laser Tube

A glass tube located at the rear of the laser unit that generates the laser beam.

103. Resolution

Resolution (expressed in dpi) is defined as a parameter that controls the intensity of laser spots per unit area 44.

104. Off Shade

The standard shade or color of denim clothes is required by all buyers. Off shade occurs when the shade/color falls short of or exceeds the buyer's expectations. Overwashing is the most common cause of off-shading. It can also be caused by using too many or too few chemicals, using too high or too low a temperature, using too much or too little pressure, using too much or too little tumbling, using unstable PH ranges, using incompetent operators, and so on 45.

105. Yellowing

When bleach is used, it is common for yellowing to occur. Excessive use of sodium hypochlorite in bleach washing is the most common cause of yellowing in denim clothes. The presence of residual chlorine in sodium hypochlorite causes yellowing. Yellowing can be caused by unremoved impurities or metallic/mineral content in pumice stones. Softening agents can also produce yellowing. Furthermore, pollutants/gases in the air might exacerbate the yellowing of washed denim during storage. When denim items are washed incorrectly, the optical brightening process causes yellowing. Furthermore, if the washing water has a high concentration of calcium or magnesium ions, the denim will yellow 45.

106. Washing Damage

When denim clothes are damaged as a result of washings, this is referred to as denim garment washing damage. When washing denim, the washing machine's very sharp elements may come into touch with the denim clothes, causing washing damage. Furthermore, while washing with stones, the stones may become abraded along with the denim garment. Overtime washing, over tumbling, overpressure on denim items, uneven machine running, and other factors can cause damage 45.

107. Washing Mark

Washing marks occur by different kinds of washing machines at different washing stages. A washing mark is a lengthy area that forms in denim garments after they have been washed. Washing marks are commonly encountered in stone bleaching and stone abrasion processes during stone washing. The high abrasion of stone in washing machines, as well as the irregular size of stones, can cause washing marks. The stiff (synthetic fibers) fabric abrades with the washing machine during denim washing, resulting in the washing mark. During production and transportation of denim fabric, automatically produce creases in denim fabric. These creases will appear as a washing mark if they are not removed from the denim fabric before washing. Denim clothing have loose and lengthy threads that are not properly removed. The loose and long threads entangle the denim garments during the washing process, resulting in washing marks. The amount of water used for washing is either too much or too little, resulting in a washing mark. During denim washing, there are additional washing marks caused by insufficient hydro extraction, incorrect drying time, and drying temperature 45.

108. Washing Spot

Washing spots are most commonly caused by excessive amounts of chemicals in washing machines. These defects may occur for the washing machine operator. Furthermore, washing spots occur when any of the washing machine's fragile parts break and fall into the washing system. Washing spots can also be caused by a high pH level, overheating, or washing for an extended period of time, among other things. Occasionally, bleach chemicals are dropped on denim garments without care, causing spots on the garments 45.

109. Over Washing

It is vital to use the correct temperature, washing time, and PH in the washing machine when doing washing. Denim garments washing maintains an optimum limit of temperature, washing duration, and PH, and when it exceeds this limit, overwashing occurs 45.

110. Color Bleeding at Pocket Bag

Color bleeding in the pocket of denim clothes can be caused by a variety of factors. When the washing temperature is too high or too low in the case of enzyme washing, the enzyme becomes deactivated or inactivated, resulting in color bleeding at the pocket. These flaws occur when hydro extraction is not done effectively (water content in denim clothing remains high) and the stacking period of hydro extracted fabric is too long. When utilizing washing chemicals, if the chemicals are not good or have lost their basic function, several defects will occur. These defects can also be caused by drying too many denim clothing at once and at too high a temperature. These defects can also be caused by insufficient rinsing and washing machine rotation during rinsing 45.

111. Lycra Problem

It's a typical issue when it comes to washing jeans. Damage Lycra or Lycra coming out in the washing of spandex fabric. This is visible extensively just after garments washing. Lycra breaks down when exposed to high temperatures, such as in a heated chamber or a steam compartment. Alkali, chlorine bleach, and abrasion are all very harsh on it. Spandex filaments can be missed through the width.

112. Crease Mark

In the washing industry, crease marks on textiles are a typical occurrence. Some techniques used to reduce this problem during washing. Generally technician used Anti crease agent or Lubricant agents. This problem may be come, for example, because of less amount of water, overloaded garments, high temperature, high RPM of machine.

113. Monkey Wash

It utilizes potassium hypermanganate in combination with oxalic acid for fading.

114. Kingpins Show

Kingpins Show is a trade show for the denim industry. For professionals in the denim industry, the Kingpins Show is the most important event of the year. This trade fair runs in New York, Hong Kong and Amsterdam, which is cementing its status as a fashion capital.

115. Eco-Clock

The Eco-Clock, from Jeanologia, is a tool that allows obtaining live information about energy, water and chemicals consumption during the jeans finishing process, and it compares the results with those that would be obtained if the same processes were carried out with sustainable technologies. This tool is aimed at making the industry and consumers aware of the importance of improving the production processes, turning them into more sustainable ones 46.

116. Pumice Stones

A small, lightweight piece of hardened lava foam used in the process of pre-aging denim called vintage wash or stonewashing. Tough, porous and lightweight, larger pumice stones are also used to de-pill sweaters and as an abrasion agent to distress target areas of jeans 4.

117. Railtracks (Train Track Fades)

The fades along the outseams of jeans, which resemble a train track. Railtracks occur when the fold of the outseam presses up against the bordering fabric causing fiber damage and dye loss. They are an interesting, albeit less common fade pattern as they occur mostly in selvedge denim and slim fits 4.

118. Denimhead

A special breed of (usually male) connoisseur who is passionate about indigo, selvedge and raw denim. Engaging in obsessive behaviours to get great fades, many denimheads rarely wash their jeans 33.

References

1. Denim Dictionary. Retrieved from https://tenuedenimes.com/pages/denim-dictionary#worn-in-denim
2. Denim Methods. Retrieved from https://www.methodofdenim.com/blogs/your-denim-your-dna/denim-methods
3. Denim – Construction and Common Terminology. Retrieved from https://onefamily.lfapps.net/sites/default/files/learning/merchandising/Denim%20and%20washes.pdf
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8. Javed Sheikh, Indrajit Bramhecha, Chapter 6 - Enzymes for green chemical processing of cotton, Editor(s): Shahid-ul-Islam, B.S. Butola, In : The Impact and Prospects of Green Chemistry for Textile Technology, Woodhead Publishing, 2019, Pages 135-160, https://doi.org/10.1016/B978-0-08-102491-1.00006-X.
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18. Khajavi, R., Novinrad, B., & Kiumarsi, A. (2007). The effect of ultrasonic on the denim fabric worn out process. Pakistan journal of biological sciences : PJBS, 10(4): 645–648. https://doi.org/10.3923/pjbs.2007.645.648
19. Muhammet, U. (2013). Ultrasonic Washing Effect on Thermo Physiological Properties of Natural Based Fabrics. Journal of Engineered Fibers and Fabrics. https://doi.org/10.1177/155892501300800105
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27. Maurice Malone, The anatomy of aged jeans & replicating fading, Apr 2017, williamsburggarment.com, Available from https://williamsburggarment.com/raw-denim/anatomy-aged-jeans-replicating-fading/
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4. Laser Washing

Alternative denim washing processes with the least amount of environmental effect from the denim industry have become a major goal. The utilization of laser technology to simulate the human hand is the most current advancement in denim processing. It is the denim finishing market's fastest growing and most widely accepted new technique. Sublimation, or the process of dissolving indigo from a solid to a gaseous state by heat, is how laser technology removes the indigo color from denim fibers. Laser technology now allows for accurate replication of old appearances. The application of Laser technology to denim washing has the ability to transform the process from one that is more conventional to one that is more modern and environmentally friendly. Lasers become a powerful tool in creating unique goods for niche and exclusive markets when they are supported by comprehensive, design-focused integrated software systems. The purpose of this article is to summarize the principle of laser fading on denim items, as well as to discuss the benefits and drawbacks. In addition, the most recent advances are briefly highlighted.

4.1 Introduction to Laser Washing

Since the nineteenth century, lasers have been employed in the textile industry for a variety of garment production applications 1. In the apparel and textile industries, laser technologies are utilized to create micro and macro effects on textiles. Laser can be employed at the micro level to change the structure of common fibers, yarns, or threads in the process of developing innovative textiles; structural modifications result in new properties and wider use of materials 2. Laser Marking (only the fabric's surface is processed, fading), Laser Engraving (controlled cutting to a depth), Laser Welding (a molten material joins or welds two or more layers of fabric together), and Laser Cutting (cutting through a fabric) are some of the most common applications of lasers 3. The schematic representation of certain laser treatments is shown in Figure 4.1.

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Figure-4.1 Schematic representation of some laser treatments 4.

Fading is the most common and environmentally friendly dry technique in the denim industry today 2. It is a well-known method for enhancing the appearance of fabric on the outside. On denim fabric, various sorts of fading processes are used to alter the cloth's outside surface 5. Faded or distressed denim effects are currently achieved industrially using a variety of physical, chemical, and mechanical finishing procedures that can pose serious health dangers to those working in and living near fashion manufacturing centers. Indeed, employing traditional technologies to create faded and ripped effects in denim necessitates a considerable amount of water, the majority of which is polluted by chemical compounds used in denim fabric manufacturing. Laser technology has been widely utilised to replace these types of traditional methods 2. Discoloration, abrasion, decorating, marking, engraving, and cutting are all old methods that can be completely replaced by laser 6. Laser technology in textile manufacturing does, in fact, open up new possibilities for denim washing.

The use of laser in denim engraving has exploded as a way to add value by substituting traditional denim-distressing techniques, which will elevate the denim segment to a level of sophistication that non-laser methods can never achieve 1. The introduction of laser technology has resulted in significant advancements in the industry by drastically reducing water waste. For example, Levi's has teamed with Jeanologia, a Spanish industrial laser specialist, to digitalize the denim finishing process, attaining their aim of zero chemical discharge by 2020 6. In fact, this technology has redefined the future of denim as a whole. It has also enabled perfect alignment with the green industry idea, resulting in cleaner manufacturing with improved chemical, waste, and energy management. It is a process that will, in the future, fully replace other washing processes.

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Figure-4.2 An ordinary light and a Laser beam 1.

4.2 Principle of Laser Technology

A laser is a device that brings light via an optical amplification process based on the stimulated emission of electromagnetic energy. "Light amplification by stimulated emission of radiation" is the origin of the name "laser." Figure 4.2 depicts the difference between conventional light and a laser beam. Lasers work by generating a lot of heat. The material is subjected to intense heating in a very small area within the targeted region. The substance is swiftly heated as the laser energy is absorbed as heat. There is a phase transition from solid to liquid. The remaining liquid boils and releases fumes as it heats up quickly. As seen in figure-4.3, another phase transition occurs from liquid to gas 2. The wavelength of the laser determines its color. The nanometre (nm) is the most extensively used unit for expressing a laser's wavelength 1.

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Figure-4.3 Laser washing of denim [3,6].

CO2 lasers are mainly formed by passing an electric discharge through a gaseous mixture that has been stimulated with direct current (DC) and radio frequency (RF) radiation. The CO2 laser is a gas laser that uses CO2, a medium for lasers with a wavelength of about 10.6um. When a high voltage is applied to the electrodes, discharge across the cavity excites CO2 molecules, resulting in laser light that can be directed towards treated materials 6.

Designers can change the aesthetic of the etching by changing the intensity of the laser beam, which can range from little surface damage to complete burning of the textile fabric. One of the best fabrics for etching and producing surface effects is denim. Material testing is critical for reaching the intended appearance, as settings like power, speed, and frequency levels may need to be modified based on fabrication and product design 7. Some laser treatment parameters have an impact on the mechanical, chemical, and color aspects of denim cloth. Pixel time (expressed in µs) is a parameter that regulates the amount of time it takes to place the laser beam at each image location 2. 100 and 150 µs pulse times were shown to be adequate for optimal fading process conditions in terms of both color and mechanical qualities 8. The third parameter is resolution (in dpi), which is defined as a parameter that determines the intensity of laser dots per unit area 2. Modern laser machines have a z-axis that moves up and down automatically to etch a variety of shadowed and textured patterns with distinct layer and color transitions 6. A laser engraving system typically includes the following components: i) a beam delivery system, ii) a work bed on which the materials to be processed are put, iii) fume extraction devices, and iv) a housing that encloses the system. Laser engraving systems include three different types of work beds. The bed could be made of honeycomb, metal slats (with microscopic holes), or metal rods (also containing tiny holes). The rationale for this is that fume extraction is frequently performed from beneath the work piece, and the openings or holes allow gases to circulate as processing debris is taken away from the work area. This also allows the cloth to be held through suction onto the work area during processing 9.

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Figure-4.4 Laser engraving on denim & jeans 10.

4.3 Laser Based Denim Fading

The sandblasting method of fading denim is being phased out in favor of the new laser fading technology. The denim washing process begins with the development of a digital file that is illustrated in a way that the laser can understand. The garment can be laid flat or stretched vertically to allow the laser to engrave across it. Figure 4.5 depicts a simple setup for a laser-based fading system. In laser fading, a computer directs the laser beam to the substance that has to be marked or faded. Carbon dioxide (CO2) lasers are particularly well adapted to laser treatment of textiles. CO2 lasers use a mirrored tube to contain a combination of gases such as CO2, nitrogen, hydrogen, and helium.

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Figure-4.5 Simple setup for laser-based fading system 11.

The gas creates thermal energy when it is activated by an electrical current, which is reflected by the mirrors and increased, resulting in a laser beam from one end of the tube. Laser treatment can only take place if the laser beam is focused at the textile surface. The component that permits the laser beam to move across the surface is the laser scanning head. Two galvanometric mirrors and one z-linear optics make up the scanning head's major components. The laser beam is directed along the X and Y axes by the galvanometric reflectors. This movement is carried out at an high rate. The laser beam is kept focused on the work area thanks to the z-linear optics. Because the distance between the laser and the surface changes over time, the beam must be refocused on the surface on a regular basis in order to concentrate its energy on the correct place. The z-linear optics allow the laser beam to remain focussed by adjusting its focal length in real time. Galvo lasers are extremely rapid and efficient methods for distressing and finishing textiles because the laser head does not physically move. These methods can age and distress products. The dye is decomposed by the laser beam. The dye is decomposed by the laser beam, and the resultant fumes are expelled. Only where the beam hits the fabric does the material discolor.

There are two types of lasers employed commercially: solid-state (wavelength of 1 μm) and gas-state (wavelength of 10 μm). The wavelength, power density, and pulse width of the laser beam determine the desired degree of fading. When compared to acid washing or sandblasting, laser marking or fading is more environmentally friendly. Aside from changes in laser power (measured in watts), the intrinsic characteristics of most textile laser systems are very comparable. The software interface and capabilities, the system's efficacy over time, and the required production capacity are all important differentiators amongst textile laser systems. Most machines are now Industry 4.0 and have circular material feeding processing techniques, which allows a single operator to load regularly such that the positioned garment moves forward in the belt as the operator arranges the next garment. Most wash effects, such as stone wash, mill wash, moon wash, bleach, PP spray, monkey wash, cat whiskers, snow wash, holing, tinting, and so on, have been replicated using this technology [1,6,10 12, 13]. The laser can consistently produce high-resolution half-tone images on denim, giving designers the ability to add bespoke faded designs, patterns, or writing to clothing. Figure 4.6 depicts denim samples that have been laser faded.

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Figure-4.6 Laser Faded Denim.

4.4 Software for Laser Fading

The system's brain is software. Manufacturing software that is oriented on the production process can perform miracles. The laser source's power, the galvanometric mirrors' speed of movement, and the focus are all controlled by software. The software essentially transfers data inputs to the system in the form of drawings and projects, which was created in the most common design software in surface drawings. The software may achieve effects such as lived effect, various forms of discoloration, tactile effects, engraving of designs and patterns, and engraving of various sorts of images by changing the laser parameters. BMP, AI, DST, DXF, PLT, DWG, HPGL, WMF, DSZ, PNG, JPG, TIF, PCX, GIF are just a few of the image formats that have been added to the software [1,6,10,12,14].

CarbonLaze is an online software application developed by RevoLaze, LLC, a laser technology company, with the goal of considerably reducing the time it takes to create laser design files while also giving them a more authentic and natural appearance. The procedure is straightforward: i) taking a high-resolution photograph of the denim garment, ii) uploading the photo to CarbonLaze, and a laser file is created in minutes. Laser designers can also use Photoshop to make slight changes to the CarbonLaze laser file if necessary. CarbonLaze files will open in Photoshop and work on any laser system currently on the market because they are standard laser files. A file that could have taken an entire day to draw took only a few minutes now 15.

The Jeanologia softwares are designed for laser textile design, are multilingual, simple to use, and include a vast portfolio of laser designs that is continually updated, exclusive, and fashionable, and can provide endless creative and sustainable options. The new software eMark 5, eDesigner allow to create a laser design from scratch or update an existing one (e.g., shown in figure-4.7). From textures, tears to washing effects, laser and jeans designers can boost their creativity and production more quickly and easily 16.

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Figure-4.7 Designing laser effect in software 16.

VAV Technology's Fabro-Tech is a revolutionary denim design program that gives the material a highly natural fabric spectrum with distinctive effects like thin slub effects (as seen in figure-4.8) and ring effects. This innovative technique allows denim manufacturers to design and modify distinct denim looks, as well as offer the material a more qualified and valuable character. Wilma7 is also a new VAV Technology denim design software that gives the material a highly natural fabric spectrum with a variety of unique effects 17.

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Figure-4.8 Thin Slub Effect 17.

[Image Courtesy: http://www.vavtechnology.com/media/print/Fabrotech.pdf]

Tonello's CREA software 18 and RAYLASE's Rayguide 19 both have a wide range of functions and are continually being updated with new ones. Cameras and image processing software are used in some new laser etching machines to automatically align patterns 18.

4.4.1 File Types

Rows and columns of square pixels constitute bitmap graphics. Each pixel has a numerical color value and is mapped. To determine the intensity for marking each pixel, laser marking software examines grey scale values. Microseconds (s) are used to measure pixel time. The laser will stay in that location for longer if the pixel is darker. The grey scale ranges from 0 to 255, with 0 representing black and 255 being pure white. The laser marking threshold color can be adjusted lower than 255 to permit the software to skip some bitmap data and speed up the marking activity. Although it is typical to set the threshold limit to 220, the suitable threshold color limits vary depending on the textile substrate and laser. Figure 4.9 depicts an enhanced view of pixels in a greyscale bitmap image.

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Figure-4.9 Enhanced view of pixels in a grey scale bitmap image 18.

The laser beam's point of contact has a dimension that is commonly referred to as kerf. The term "kerf" comes from the woodworking industry and refers to the width of a saw blade. The laser beam will make overlapping contact on the fabric surface if the resolution in pixels per inch is finer than the kerf of the laser (as seen in figure-4.10). If the marking intensity is strong enough, this might cause physical damage to the substrate as well as ignite.

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Figure-4.10 Representation of varing the resolution of a bitmap image while the laser kerf remains constant 18.

On the other hand, lines with mathematically determined magnitude, direction, and location constitute vector graphics. The laser marks vector files by operating continuously while tracing over solid lines. The duty cycle of the laser and the laser's marking speed affect the intensity of the laser marking. The amount of energy released by the laser can be reduced by lowering the duty cycle %. Marking at a slower speed will etch or cut more deeply. Vector marking files should be structured in such a way that lines do not cross. Re-marking an area that has already been marked is likely to harm the substrate and may result in ignite. For the same reason, abrupt changes in direction should be avoided 18. Figure 4.11 and 4.12 show the effect of marking a vector design with different speeds for adjacent lines, and figure-4.13 shows the results of laser etching using this approach.

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Figure-4.11 Representation of a vector design with color coded lines for variable marking speed 18

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Figure-4.12. Cross section of the vector design in Figure 4.11 18.

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Figure-4.13. Demonstration of the results achieved by varying the marking speed of lines in laser vector files 18.

4.5 Laser Patterns

A laser can be used to mark patterns and photo realistic images. The most common method is to use bitmap files. The fabric's features limit the amount of distinct grey scale values that can be created by laser etching. On indigo ring dyed denim, six to eight different hues can be predicted 18. The dye on the surface of the denim fabric is vaporized by the laser irradiation of a dynamic CO2 laser marking machine, resulting in a fade-free visual pattern, a progressively changing flower shape that adds fresh eye-catching aspects to the denim trend. Laser engraving technique combined with artistic denim fabric finishing creates artistic patterns on the fabric, which can incorporate text, numbers, logos, photos, and more. The laser engraving machine can also make monkeys, cats whiskers, tattered, worn, and other effects using precise cutting technology. To strengthen the creative impression, these patterns can be embellished with embroidery, sequins, ironing, and metal accessories (as shown in figure-4.14) [20-22].

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Figure-4.14 Laser patterns in denim items 23.

4.6 Influencing Factors of the laser treatment

Material, laser Source, technological process, and complex influence are the four groupings of factors that influence the laser treatment process 4.

Reflectivity is a function of the wavelength of laser radiation R = R (λ). The laser effect on a substance in falling radiation varies depending on the materials and is connected to radiation reflection and absorption. The figure-7 shows that Colored light is reflected from the amorphous part of the fabric, where the dye molecules are bonded to the fabric's fiber molecules, while white light is reflected from the surface. Reflection from the surface and transmission through textile threads can both cause laser energy to be lost. To accomplish the laser process, the material's high absorption necessitates a low beam power.

Textile materials undergo micro and macro structural changes as a result of heat treatment. Heat transfer occurs in the treated region during the laser marking process, therefore basic thermal physical properties such as thermal conductivity coefficient, specific heat capacity, and coefficient of thermal diffusivity must be considered. Furthermore, laser processing of materials relies on achieving high temperatures, which causes changes in the structure and elasticity of the materials being processed. Each material's elastic behavior is defined by its modulus of elasticity (Young's module). The modulus of elasticity and plasticity of materials are both affected by temperature. As the temperature rises, the modulus of elasticity falls and the plasticity rises. Figure-4.15 shows the complexity of the laser beam interaction with painted fabric that contains dye molecules.

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Figure-4.15. Interaction of a falling light beam with textile material 4.

The laser beam's penetration depth in the treated material is the distance it travels. As the depth of penetration increases, the energy of the laser beam decreases. It's because of the fabric's scattering and light dispersion. The wavelength of the laser source is the most important factor in ensuring light photon absorption in the material and its capacity to do so at the desired depth. In this regard, the material's composition, structure, and density all have a role. The wavelength of the laser source has an inverse relationship with the penetration depth. To a large extent, it is determined by laser power; that is, the more power the laser has, the more profound the changes in the material are.

On the global market, a wide range of laser sources and laser technology systems with various characteristics and applications are available. As a result, a laser with good beam quality and a wavelength that will be appropriately absorbed by the specific material in each situation must be chosen. The wavelength – is the most important feature of any laser. It determines the laser beam's ability to concentrate. The wavelength affects the absorption and reflection properties of the relevant materials. The absorption coefficient and penetration depth are both functional in relation to the λ. The CO2 laser at 10600 nm is ideally suited for this application because of the organic material characteristics of denim.

With the focal optics (lenses or mirrors) for each laser system, the laser beam focuses on the treated surface in a spot of a specific diameter, known as the minimum focal spot diameter. It is determined by the wavelength – λ, the beam diameter, the focal length, and the beam propagation ratio. Laser treatment of textile materials, on the other hand, is done with laser sources that work in pulse mode. Pulse power, pulse energy, pulse duration, frequency of pulses, and the interdependencies of these factors with the average power of the laser are much more significant. Marking, for example, necessitates longer pulses with lower pulse power than engraving.

In the domain of marking, the surface power density is a crucial factor impacting the structural or phase transitions of the material. The surface power density is directly functionally reliant on the average power of the laser source and inversely proportional depending on the area on which the beam falls. Each laser source's average power, and hence its power density, are specified in the manufacturer's technical specifications and cannot be changed. As a result, the size of the circle generated by the laser beam, known as a focal spot, will determine how this parameter is optimized. The surface density of power will fluctuate as the diameter of the focal spot changes. The Surface density of power will be greater for the same average radiation power when this beam is focused in a smaller area.

The motion of the laser head is referred to as marking speed, and it is crucial to the precision of the processing. When the speed of the laser beam is higher, the duration of impact is shorter and the energy absorbed by the material in the impact area is lower, and vice versa. The technological process, on the other hand, is more effective when the laser beam speed is higher. The number of laser beam repetitions for marking and engraving is also a significant component. For some materials, it is preferable to engrave with low power and high speed and then repeat the procedure numerous times. Textiles that are processed at high power and low speed cause more fiber damage than textiles that are treated at lower power and higher speeds. It may be necessary to re-pass the laser beam to acquire the desired effect 4.

4.7 Advantages of Laser Finishing

When it comes to denim fading, there are various advantages to employing laser versus traditional methods. The following are some of the primary advantages of laser denim finishing [6, 22]:

- The design choices are endless, resulting in a more accurate, consistent, and defect-free wash effect. Depending on the necessity, the designs can be placed wherever on the clothing.
- Because it is a physical rather than a chemical process, there is no need for pre- or post-processing of the fabric or garment, and it may be done even on the finished product.
- Technology is progressing to the point where the machine can be automated and integrated with various online processes.
- It is a significantly faster method than traditional fading since it eliminates the need for many wash processes, which reduces production time.
- It may be created to work with a variety of materials, including wood, paper packaging, plastic products, label paper, leather, cloth, glass, ceramics, resin, bamboo products, and PCB panels, among others.
- This procedure is completely environmentally friendly, requiring very little water and no chemicals.
- Eliminating numerous wash and finishing phases has resulted in a significant reduction in labor and process costs, lowering manufacturing costs tremendously.
- Protects denim fabric from damages caused by traditional tools, chemicals, stones and bleaches etc.
- There is comparatively less strength loss with low hairiness because no forced handling is necessary, which is not the case with stretch denim.
- Industry 4.0 ready as well as compatible with the traditional manufacturing process, as newer machines are equipped with conveyor systems, and the only human requirement is to place the denim in the projected position.
- Using a software library, quickly achieve wear markings and controlled breakage on textiles, as well as varying levels of ageing effect on clothing that may be reused in the future activity.
- It can completely obviate the requirement for inventory because any number of finishes can be replicated using only a laser file and a post wash, paving the path for On-Demand Manufacturing.
- Because there is no change in pH value throughout the fading process, a laser treated denim garment can be worn immediately after the fading process.
- Laser washing is combined with some traditional procedures to create distinctive high-end boutique denim.
- The finished laser engraving product offers a highly uniform effect, as well as an exact and consistent quality, whereas quality is difficult to control in traditional manual work.

4.8 Disadvantages of Laser Washing

The most significant disadvantage of this method is its relatively expensive cost. The machine requires skilled operators to operate, which might be a disadvantage at times. In addition, the laser system has a larger power consumption. Using laser finishing to create a natural-looking effect on denim could be a challenge. Sometimes, even after a laser finish, some designs or fading require a hand touch to achieve a natural look, which eliminates the need for a laser in the first place. The gases released during the procedure are hazardous to one's health, and laser radiation is toxic to the eyes and skin.

4.9 Machinery for Laser Finishing

Apart from changes in laser power (measured in watts), the underlying features for the most cloth laser systems are very comparable. The software interface and capacities, the system's reliability over time, and the required productivity are all fundamental identifiers between textile laser systems 12.

4.9.1 Laser Blaze

Tonello's Laser Blaze is the company's most recent laser machine model. Through the use of a laser beam, the machine can mimic vintage effects such as localized wear, whiskers, and breakages. Patterns, deceptive holes, patches, and astonishing tridimensional effects can all be created using it. Laser Blaze stands out for its ability to treat all positions of jeans, resulting in a true, worn-in appearance and great uniformity throughout the working area.

Abbildung in dieser Leseprobe nicht enthalten

Figure-4.16 Products from collection Prism by Tonello®, made by Multicolour Laser Technology 24.

4.9.2 Multicolour Laser Technology

Multicolor Laser is a true revolution in the laser finishing industry since it entirely transforms the laser concept. Multicolor Laser is the product of a careful analysis integrating Zaitex's proprietary resin with Tonello's environmentally friendly technologies. The multicolor laser technology employs a unique resin that is applied to fabric using Kit Batik and then securely imprinted on the cloth with a special setting of the Tonello laser. The technology assures penetration while also lowering waste. On a variety of fabrics, including denim, leather, and seamless cloth, the laser can generate color and contrast effects. To welcome the new development, Tonello Research has developed the Prism collection, which highlights two of the company's most sustainable technologies, Kit Batik and Laser Blaze, and displays the full range of effects (e.g., shown in figure-4.16) that can be achieved by combining the special resin with Tonello technologies [24, 25].

4.9.3 Jeanologia’s Laser Technology

Jeanologia, a Spanish company, is a pioneer in the development of sustainable garment finishing technologies, with solutions based on laser that can boost productivity, shorten time to market, and lower manufacturing costs. Nano laser technology, compact laser technology, laser pro technology, and high dynamic range (HDR) laser technology are all available from Jeanologia. These laser technologies, according to this company, suit the needs of large production, with versatile cloths and detailed and accurate designs 26.

4.9.4 Arges Laser System

Arges, a laser system from Turkey, is built with galvanometric motor technology and can provide laser beams in milliseconds in any required spot diameter, to any intended point, and at any requested time, allowing users to function at maximum capacity and eliminating performance-related time wastage. The 3D+ Optical System, which was devised for smoother design transitions, finer lines, and greyscale, and the Arcon software that operates the laser, which can process a wide range of file types, are two notable characteristics. Arges Laser technology is also environmentally benign and energy efficient, making it a strong choice for sustainable washing systems [12, 14].

4.9.5 F.L.X. technology

Levi Strauss & Co. unveils Project F.L.X. (future-led execution), a laser-powered technology that allows customers to customize and personalize their jeans with a distinctive distressed appearance. Project F.L.X. cuts time to market in half and removes tens of thousands of chemical formulations from the jeans finishing process.

4.9.6 Renowned Companies

Abbildung in dieser Leseprobe nicht enthalten

4.10 References

1. Nayak, Rajkishore & Padhye, Rajiv. (2016). The use of laser in garment manufacturing: an overview. Fashion and Textiles. 3. 10.1186/s40691-016-0057-x.
2. Dalbaşı, E. S., Özçelik kayseri, G., & İlleez, A. A. (2019). A research on the effect of various laser fading parameters on physical and surface properties of denim fabric. Optics & Laser Technology, 118, 28–36. doi.org/10.1016/j.optlastec.2019.04.030
3. Khalil, Elias. (2015). Sustainable and Ecological Finishing Technology for Denim Jeans. The American Association for Science and Technology (AASCIT). 2. 159-163. 10.6084/M9.FIGSHARE.1480400.
4. Angelova, Y. P. (2020). Factors influencing the laser treatment of textile materials: An overview. Journal of Engineered Fibers and Fabrics. https://doi.org/10.1177/1558925020952803
5. Solaiman, Joykrisna Saha, Comparative Analysis of Manual Fading and Laser Fading Process on Denim Fabric, Science Discovery. Vol. 3, No. 6, 2015, pp. 44-49. doi: 10.11648/j.sd.20150306.11
6. It is in Your Jeans, September-2019, TANTU Annual Journal 2019 on seventh edition of TANTU.
7. Unal F., Yavas A., Avinc O. (2020) Sustainability in Textile Design with Laser Technology. In: Muthu S., Gardetti M. (eds) Sustainability in the Textile and Apparel Industries. Sustainable Textiles: Production, Processing, Manufacturing & Chemistry. Springer, Cham. https://doi.org/10.1007/978-3-030-37929-2_11
8. Ozguney, Arif & Özçelik, Görkem & Özkaya, K.. (2009). A study on specifying the effect of laser fading process on the colour and mechanical properties of the denim fabrics. Tekstil ve Konfeksiyon. 19. 133-138. https://dergipark.org.tr/tr/download/article-file/218103
9. Joy Sarkar and Md. Rashaduzzaman, Laser fading technology: facts and opportunities, August , 2014. https://www.textiletoday.com.bd/laser-fading-technology-facts-and-opportunities/
10. Md. Raisul Islam Rifat, CO2 Laser Galvo Systems for Laser Marking and Engraving on Denim & Jeans, May, 2021. textileblog. https://www.textileblog.com/laser-engraving-on-denim/
11. Shafayat Hossain Enam, Flow Chart Of Laser Finish, Textile Study Center, https://textilestudycenter.com/laser-in-denim-industry-laser-finishing-method-flow-chart-of-laser-finish/
12. Dr. Traci A.M. Lamar, Laser Finishing For Textile Materials, July 23, 2020. https://www.textileworld.com/textile-world/features/2020/07/laser-finishing-for-textile-materials/
13. CO2 galvo laser marking and engraving on jeans and denim cloth, https://elenlaser.com/blog/co2-galvo-laser-marking-engraving-jeans-denim.html
14. https://www.best.com.tr/en-us/products/denim-marking-machines
15. From Picture To Laser: A New Tool By RevoLaze, une 18, 2019. https://www.denimsandjeans.com/denim-fabric-developments/picture-laser-new-tool-revolaze/39207
16. http://www.ptj.com.pk/Web-2019/01-2019/Denim-Fabrics-and-Apparel-Jeanologia.html
17. http://www.vavtechnology.com/media/print/Fabrotech.pdf
18. Laser Applications on Cotton Textiles, TECHNICAL BULLETIN, 2020. Cotton Incorporated. https://www.cottoninc.com/wp-content/uploads/2021/02/TRI-4011-Laser-Applications-on-Cotton-Textiles.pdf
19. https://www.raylase.de/en/products/software/software-RAYGUIDE-1.html
20. Laser Engraving Denim Jeans Processing, Golden Laser. https://www.goldenlaser.cc/solutions/laser-engraving-denim-jeans-processing
21. Laser Processing For Denim, Oct 26, 2020 . https://www.cklasermachine.com/info/laser-processing-for-denim-50818898.html
22. https://www.goldenlaser.cc/laser-solutions/denim-jeans/
23. Jeans laser engraving, deduces new trend of denim, Aug-19-2019, Golden Laser. https://www.goldenlaser.com/blog/jeans-laser-engraving/
24. https://www.tonello.com/en
25. Sjolrivet, Tonello Introduces Multicolor Laser for Denim and More, March 2015. Https://sourcingjournal.com/denim/denim-brands/tonello-introduces-multicolor-laser-for-denim-and-more-98208/
26. https://www.jeanologia.com/

5. Cutting Edge Technologies

Traditional denim washes, which required harsh chemicals and a lot of water to get an aged and worn-in effect, were bad for the environment. In the field of denim washing, innovative approaches are constantly emerging to address the limitations of traditional washing processes. In reality, enterprises across the denim supply chain are launching innovative sustainable ways to streamline existing operations. Though detailed descriptions of many recent washing methods are not provided, the purpose of this article is to showcase the available cutting-edge denim washing technologies.

5.1 Introduction

Denim fabric washing has progressed significantly in recent years. There are distinctive washing treatments that increase the performance of the denim fabric and the final impression on the garment, in addition to traditional ones that provide standard quality. In today's denim market, washing is a point of differentiation. As a result, producers all over the world are always attempting to introduce innovative concepts in the field of denim cleaning, ensuring customer satisfaction while also conserving the environment. However, in order to create anything unique, one must first understand the accessible technology. In that light, the following is an attempt to review the cutting-edge technology offered by various companies around the world. Finally, it's worth noting that, despite the fact that there are numerous machine makers on the market, only a few technologies are included here.

5.2 E-Flow technology

Water is traditionally utilized as the carrier, and at the end of each cycle, that water, which is still brimming with chemical compounds, is discarded. However, by using nanobubbles of air instead of water, JeanologiaTM's e-Flow Technology replaces standard abrasion methods while giving greater performance chemistry (color, softeners, antimicrobials, and so on). This method is based on air nanobubbles (1000000 bubbles/cm3) that operate as a transporter for chemicals to be transmitted into a garment. With the greatest quality, the least amount of water, and zero discharge, e-Flow technology can achieve a wide range of finishing effects [1-2].

5.3 Enzyme Spray technologies

Novozymes devised a way in 2017 to spray enzymes directly on denim in a closed washing machine system rather than adding the enzymes to an open washing machine, reducing the amount of water needed for the enzyme wash even further. As a result, when enzymes are sprayed, the have the potential to create safety issues when sprayed. It confirms that enzyme exposure limits aren't surpassed. When compared to traditional washing machines, the DeniSafe® system, which uses enzyme spray technology, can save up to 90% of water. Because the fabric is just misted with water rather than soaking in the washing machine, this is the case. I It might also save money on chemicals. The enzyme action is boosted by the system's low water levels. As a result, complete pumice stone replacement is a possibility [3-4].

5.4 Technoflow Twin Technology

The procedure of delivering a large number of enzymes and chemicals to the washing machine through a single tank, as well as filling and emptying the chemical tank on a regular basis, has begun to put a significant amount of strain on the operators. The new 6-cylinder tank system (shown in figure-5.1), which was created to meet the needs of the second-generation Technoflow machine, eliminates this problem and decreases denim makers' operating burden. In Technoflow, 6 different enzymes can be housed in 6 distinct tanks at the same time and transported to the washing machine in the sequence required. As a result, the amount of time and money lost due to a single tank system is diminishing. The enzyme and softener are combined with water in the Technoflow and allowed to flow into the washing machine as a pulverized spray. This mixture sticks to the jeans more efficiently thanks to nanobubbles. All of these enzymes attach to the jeans since the system operates with such a small amount of water. As a result, chemicals are not thrown away with water, and a significant amount of chemical contamination is avoided. It is possible to undertake both low-water and high-water washing with the second-generation Techno Flow Machine 5.

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Figure-5.1 Technoflow Twin System 5.

5.5 Robotic Technology

Vav Technology, a denim technology company, has introduced two new robotic devices aimed at allowing the denim industry to create natural and worn appearances while minimizing the hazards to workers' health and safety. The first, a robotic arm scraping robot, is used to generate natural worn looks, while the second, a spray robot, is used to brighten denim with potassium permanganate, which is a traditional manual method that can be hazardous to human health. The clever concept is to simply mimic human behavior. The most essential component in the success of robotic technology is the clone Mac copying system. The mechanism of recording is crucial to the system's success. For recording, there is a separate module. It clones the greatest scraping or spray worker to a match. In a matter of seconds, the recorded parameters (arm motion, target coordinates, spraying distance, pressure, and duration) can be readily adjusted between different sizes of garment. One recording module can serve several robot machines, resulting in hundreds of thousands of identical jeans. Universal robotic arms have technology that is as precise and flexible as a human being. These robotic arms can reach any coordinate on the clothing since they can move like a human body [6-8].

5.6 Tonello’s Washing Technology

Tonello is a global leader in garment washing, dyeing, and finishing machinery, with a special concentration on the denim industry. Tonello, based in northern Italy, has been in business since 1981 and has earned a reputation for innovation and excellence. Sustainability has always been at the heart of this vision, and it has fueled technical advancements that enable better environmental results 9.

5.6.1 ECOfree

Tonello's research resulted in ECOfree, a new ozone washing method. Tonello took denim ozone treatment to the next level (Ecofree 2) in 2017 by combining Ofree from 2010 (ozone in the air) and Ecofree from 2013 (ozone in the water). This washing technology can treat with ozone in the air and in water. This gives producers more versatility because they can combine both procedures, ozone in the air and water, with standard washes to create new stylish effects. Tonello also receives the following benefits as a result of the new cold plasma generators: Processing durations are reduced to a bare minimum, purifying expenses are kept to a minimal, and the operator and the ultimate customer are completely safe. Tonello claims that ECOfree guarantees lower water, energy, and chemical use (50-80%) while providing more vivid denim effects (e.g., shown in figure-5.2). ECOfree creates a "worn look" on denim and dyed clothing that may be adjusted based on the application, or it can be used to remove back-staining.

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Figure-5.2 Effects of Ecofree Ozone Washing 10.

5.6.2 NoStone®+ System

The NoStone®+ system is built around a stainless-steel abrasive drum that is attached to the cylinder of the washing machine. This drum has been specifically treated to make it more or less abrasive, depending on the degree of abrasion required and hence the desired result. The NoStone® effect is similar to stone-washing and almost completely eliminates the carbon footprint (CFP) of pumice stones due to the mechanical instead of chemical nature of the procedure. Water usage, production expenses, emissions, processing time, and physical labor are all reduced with the NoStone®+ method. It doesn't cause dust or sludge, doesn't harm the equipment, and gives a consistent result in both sampling and production 11.

5.6.3 Core Technology

Tonello's Core technology is the next step in the evolution of Tonello's Batik technology. It produces a fine mist inside the drum, yielding in uniform or contrasting effects during garment finishing with low water volumes and liquor ratios as low as 1:1. The technique works with a variety of Tonello washing machines, and it may be used in any manufacturing cycle without disrupting the process. The Core technology, according to the company, provides the following benefits: product savings of 50 to 80 percent and water savings of 96 percent; reduced processing times; enhanced performance; and adaptability because the machine may be used for numerous processes. Core also may be employed to apply a variety of softeners, resins and finishes and essences [11-13].

5.6.4 UP Technology

Denim washing has achieved a significant turning point with UP, after ECOfree, NoStone®, and Core. It greatly reduces the amount of water required and lowers the liquor ratio to previously unheard levels, saving both water and energy and allowing water to fill and drain more quickly. UP is a game-changing invention that works with all Tonello machines. The machine receives a consistent, regular supply of water, which is subsequently collected and recirculated. Water conservation now goes hand in hand with lower energy use and faster water filling and draining times. All of this, of course, equates to cheaper expenses. The combination with other Tonello technologies, like ECOfree for ozone washing and NoStone® for stoneless stone-wash effects, cuts expenses and carbon footprint even further [11,14].

5.6.5 All-in-One System

The All-in-One System integrates four sustainable technologies into a single machine to accomplish all washing operations: ECOfree 2, which employs ozone in the water as well as the air; NoStone® for true stone-wash effects without pumice; UP for washing methods that use at least 50% less water; Core, a nebulizing device that improves performance while lowering water usage.

5.6.6 OBleach

OBleach is a revolutionary Tonello process that uses just ozone to create an authentic, sustainable, and cool Bleach without the use of chemicals. In other words, the true Bleach without Bleach has emerged. The following are the key benefits: contrasted effects, complete respect for the fibers and the environment due to a room-temperature procedure, and maximum reproducibility, allowed by technology.

5.6.7 BATIK Technology

This equipment creates entirely new and unexpected effects like ‘rain' finishing, spots, tie-dye, and a faded appearance. There is no need for manual handling of stones in this entirely automated process, and the effect may be replicated using the Tonello software.

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Figure-5.3 Tonello Washing Machine 11.

5.7 Xeros Washing Technology

Xeros Technology Group plc is a technology platform company that is altering water-intensive industrial and commercial processes. Xeros Technology Group arose from Leeds University, where it produced a patented near-waterless washing machine based on a way of cleaning garments with a specific type of polymer.

XOrbs, XDrum, and XFiltra are the company's three core products, which it licenses to commercial washing (labelled "Hydrofinity") and apparel original equipment manufacturers (OEMs) such as Jiangsu SeaLion Technologies, IFB Industries, Ramsons Garment Finishing Equipment, Crystal International, and Midea Group. The combination of these technologies results in lower water usage, energy and chemical use, and chemical and microplastic emissions. A washing machine that uses Xeros technologies replaces 80 percent of the water consumed throughout the operation by inserting spherical-shaped polymer balls called XOrbs into the machine drum along with the clothes. At the start of the wash cycle, XOrbs are introduced from inside XDrum. The polymer spheres mingle with the clothes and massage them with a small bit of water. The XFiltra filters the water used in the cycle, reducing microfibre loss in the wastewater. After the wash cycle is completed, the XOrbs return to the XDrum automatically 15.

Xeros technologies include:

- XOrbs™
- XDrum™
- XFiltra™

5.7.1 XOrbs

The unique XOrb Polymer Technology lies at the heart of Xeros' washing system. The beads are roughly the size of a pea, Xorbs. They help to move clothes around while attracting and removing stains, dye, and dirt 16 when used with a little water. XOrbs gently clean and protect textiles and are reusable, recyclable, and safe. They dissolve into the XDrum at the start of the wash and, like tiny little hands, gently remove dirt and stains while safeguarding garments. When the wash cycle is finished, the XOrbs return to the XDrum and are ready to be used for the next wash 17. There are two forms of Xorbs: i) Nylon XOrbs (BASF supply) that remove molecules, and ii) Polypropylene XOrbs (BASF supply) that adhere molecules 18. XOrbs are used in Xeros' XDrum to provide a genuine stone wash appearance. Unlike other finishing techniques, they can be recycled into new XOrbs after a considerable number of cycles. The XOrb cycles from Xeros can be tweaked to achieve any desired product end, including stone washing, surface effects, and shading 19. Using XOrbs in the denim finishing process would eliminate the requirement for pumice stone and save 75% on water consumption. Xeros estimates that the beads can save up to 10 gallons per wash—not to mention detergent—and it may only add $50 to the initial cost of a washer [16, 20].

5.7.2 XDrum™

The XDrum technology from Xeros is a system that allows existing conventional washing machines to employ XOrbs, eliminating the need for new machines. It's a proprietary, low-cost machine drum design that allows XOrbs to be introduced into and withdrawn from process cycles in Xeros' preferred fields. Original Equipment Manufacturers can make simple updates to their devices to incorporate the Company's XOrb technology thanks to the design 21.

5.7.3 XFiltra™

XFiltra is the Company's proprietary washing machine filtration technology that prevents hazardous microfibres, such as microplastics, from being released into the world's rivers and oceans during washing cycles. Microfibers discharged into the environment during the washing of textiles and fabrics are a major source of pollution in the environment and food contamination 16.

The company's XFiltra microplastic filtration device is designed to be used in washing machines. Microplastic fibres may be removed from laundry wastewater in 99 percent of cases. The filter, pump, and de-watering device are the three main components of this system. During the production process, it can fit into any front-loading washing machine 15. Over 99 percent of the microfibres generated in a load of laundry are captured, whereas most wastewater treatment plants cannot catch these microfibres because they are too tiny. They won't wind up in our rivers and oceans thanks to the XFiltra system 22.

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Figure-5.4 Xorbs and xDrum 18.

5.7.4 Benefits of Xeros Washing Technology [16,19-20,22,]

i) Using Xeros Technologies to process and finish denim can reduce water usage by up to 60%, energy consumption by up to 50%, and chemistry consumption by up to 40%.
ii) Unlike traditional methods, Xeros carries out all operations (abrasion, bleaching, and tinting) in a single machine.
iii) XOrbs eliminate the need for pumice stone, resulting in less waste while maintaining the look and feel that customers appreciate in their favorite
iv) Because no pumice stones are utilized, there is no need to physically remove them (de-stoning), resulting in faster production times.
v) When Xeros Technologies are applied, back-staining is decreased, garment contrast is enhanced, creases is reduced, the look is better, and the results are repeatable.
vi) There is no need to handle XOrbs in the closed loop harvesting system.
vii) The procedure of adding and deleting XOrbs from the cycle is automated with XDrum denim finishing equipment. As a result, labor intensity is reduced, efficiency is increased, and expenses are reduced.
viii) XOrbs result in lower enzyme levels, such as amylase, cellulase, and peroxidase, resulting in a greener process.
ix) Xeros also created a filter to prevent hazardous microfibers from washing off garments and into water supplies.

Abbildung in dieser Leseprobe nicht enthalten

Figure-5.5 Jecostone Washed Jeans (left) & Jecorock (right) 23.

5.8 Jecostone System

Itexa Group, an Italian abrasives manufacturer, developed the Jecostone System after four years of collaboration with laundry specialists. Jecostone, an abrasive multi-fiber carpet that covers the whole drum of an industrial washing machine, and Jecorock (shown in figure5.5), a 7-centimeter-diameter abrasive pad that operates freely inside the machine in a similar fashion to pumice stones, combine to form the system. On cotton, denim, knitwear, and leather, the lightweight and long-lasting active abrasion provides unique effects, such as the iconic '80s-inspired stonewash effect for denim and a softer hand feel for knitwear 24. The negative impacts of traditional abrasives (e.g., pumice, Leca, synthetic poly-composites, minerals, etc.) are eliminated with the Jecostone® system 23. Generally, to emphasize the vintage impression, Jecorock has been combined with the Jecostone® system 23. The method is already being used by supply-chain partners across the sector, such as Diesel, which uses Jecorocks for the majority of its production in Tunisia 24.

5.9 Aqualess Mission Technology

Officina+39's Aqualess mission incorporates three process elements: Remover BC, Aqualess Aged, and Ozone Powder technology. Traditional desizing, stone cleaning, and bleaching processes can all be replaced with the Aqualess Mission technique 25.

i) Oz-One Powder

Bleached denim has been a popular fashion statement for decades, however the process of removing the indigo from denim frequently includes harsh chemicals or ozone gas, both of which are hazardous to garment workers' health and the environment 26. Meanwhile, Officina+39, an Italian sustainable chemical firm, invented Oz-One Powder, a treatment that allows laundries to obtain bleached, distressed, or acid-wash appearances on textiles using ordinary machines without water in an environmentally benign fashion equivalent to ozone 27.

The new product is chlorine and potassium permanganate-free, and it's utilized in a waterless process that may be done at room temperature by just rotating the powder with the denim in an empty washing machine. The procedure also does not necessitate the use of an ozone generator, making it more cost-effective. The Oz-One powder produces a bleached look by breaking down indigo and sulphur black dyes, as well as Officina's own sustainable dyes [26, 28]. The Oz-One particles are discharged into the tumbler, giving vintage and bleached effects similar to those achieved with chlorine or potassium permanganate 29.

ii) Aqualess aged

This waterless treatment is suitable for creating abrasion characteristics on denim, has a low environmental impact, and may be used in conjunction with Oz-One powder on both black and indigo denim 25.

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Figure-5.6 A wide range effects from washing with OZ-ONE Powder 30.

iii) Remover BC

This unique compound enhances the laser effect on indigo or dischargeable dyestuffs, saving time and energy for faster production. It also prevents fabric breaking due to the quick process, while emphasizing on a worn look 25. It can be used to boost contrast during laser treatment on denim 31.

5.10 Smart Bleach Technology

Smart bleach is a cutting-edge bleaching method for nebulizers. This cutting-edge technology was created to replace the traditional chlorine (or potassium permanganate) used in denim bleaching in washing machines. It is feasible to minimize water use by 90% when bleaching indigo and black denim using smart bleach with misting systems. Smart bleach can be used in conjunction with Novastone Nebu, a novel enzyme approved by Novozymes denisafe®, ensuring that enzymes are used safely in modern low-pressure washing machines with mist technology. A new biodegradable Reducer KM ECO neutralizer can also be used for smart bleaching 32.

5.11 Smart Foam Technology

Smart Foam is a technique developed by the chemical company Garmon to be the "easiest and most inexpensive way to save water in garment finishing." In fact, this patented process is the result of a partnership between three major garment finishing companies: Garmon, Itaclab, and Mactec 33. Smart foam introduces foam as a novel chemical carrier to treat clothing in any type of washing machine. It can be utilized to create a variety of finishes, as well as distinctive fashion concepts and designs. Its main advantage is the significant reduction in water and energy consumption: when compared to standard washing methods, the use of chemicals via smart foam allows for water savings of up to 80%. Smart foam loads chemicals in the washing machine up to three times faster than nebulization systems and doesn't require sealed equipment, allowing personnel to interrupt finishing treatments and check garments safely and easily. The smart foam equipment and technique can be used with any type of washing machine, from the most basic to the most modern. According to Garmon, some treatments, such as enzymatic washes with smart foam, generate superior abrasion when the liquor ratio is reduced. Garmon argued that with a lower liquor ratio, some treatments, such as enzyme washes with smart foam, create superior abrasion than normal treatments [34, 35].

5.12 Denethic Technology

Some companies are attempting to avoid the wash process totally with their denim textiles. Calik unveiled Denethic, a collection of fabrics with washed effects that don't require the use of a washing machine. The concept was created with the entire denim garment supply chain in mind as a way to save resources in fabric manufacture and garment laundering. Calik Denim invented the Denethic process to produce fabrics with wash effects without actually washing them after sewing, in response to a growing trend to prepare denim items with as little environmental impact as possible (or none at all). The materials are made to look like they've been rinse washed, rinse and enzyme washed, or bleached. Denethic fabrics can be cut-and-sewn or washed for a more intense wash effect, but with less water, chemicals, energy, and time. Vintage-looking and crosshatch fabrics (seen in figure-5.7) in both mid and light washes are part of the concept. Those seeking heavy wash effects for a more vintage denim look, on the other hand, can get similar effects by laundering with less water, less chemicals, and less energy than ordinary denim materials. Denethic saves 13 percent water and 16 percent of the time needed to wash the rinse look in the laundry phase. In addition, the fabric saves 13% water and 30% of the time required to complete the rinse and enzyme look. The bleached look saves the most water and time in the laundry phase, lowering 35 percent of the water used and 45 percent of the time required [36-38].

Abbildung in dieser Leseprobe nicht enthalten

Figure-5.7 Crosshatch Denim 39.

5.13 Oxygene Technology

Calik Denim developed Oxygene technology by considering the entire denim garment supply chain. The consumption of resources is reduced by oxygen during the washing stage 40. The new Oxygene textiles, which are manufactured with a revolutionary technology that blends specially dyed 100 percent cotton yarns with ordinary finishing processes, can be treated faster (approximately 50–60 percent faster than regular denim) and require fewer chemicals, water, and energy than conventional denim. Washing treatments like as laser, ozone, sandpaper, and enzymes can also be utilized. Furthermore, despite the absence of resins, treated fabrics are soft to the touch and retain their lustrous appearance following treatment 41. During the washing step, the Oxygene idea saves 95 percent of water, 50 percent of chemicals, and 79 percent of energy 42. It provides optimal outcomes (look, feel, color, and so forth) while reducing the environmental impact of washing procedures. Superior ozone wash effects; works incredibly well with laser without requiring an additional cleaning step; stronger stone wash effects in less time; offering of bright look, clear shades, natural casts, soft hand feel, and no puckering at any washing process 40.

5.14 Washpro Technology

Calik Denim's latest eco-friendly innovation Washpro technology (shown in 5.8) ensures that denim items stay fresh for a long time. End-users will require fewer washes to complete the life cycle of their denim garments thanks to Washpro technology. Washpro featured fabrics enable significant resource savings, as each household laundry consumes a lot of water and energy 38. Calik's latest Functionage textiles have anti-microbial and self-cleaning qualities, which means jeans will last longer and require less washing at home. Calik has also added DualFx technology to these fabrics to encourage long-lasting shape and better comfort. According to tests conducted during industrial washings, Washpro Technology can withstand up to 50 consumer washings 43. Furthermore, Washpro technology aids in the reduction of microfiber contamination in the seas by reducing the number of needed household laundries, hence reducing wastewater volume, which includes microfibers. Washpro's freshness feature lasts for a long time, even after industrial laundry treatments 38.

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Figure-5.8 Calik Denim’s Washpro Technology 38.

5.15 References

1. Available from https://www.jeanologia.com/
2. G2 and E-flow - bleaching jeans without chemicals, chemsec marketplace. https://marketplace.chemsec.org/Alternative/G2-and-E-flow-bleaching-jeans-without-chemicals-768
3. Enzyme Washing, Retrieved from https://en.wikipedia.org/wiki/Enzyme_washing
4. Cellusoft® for denim abrasion, https://biosolutions.novozymes.com/en/textiles/products/denim-abrasion-and-finishing/cellusoft-denim-abrasion
5. http://vavtechnology.com/green-laundry-systems/
6. John Mowbray, Tech firm turns to robots for denim effects, 29 June 2016. https://www.ecotextile.com/2016062922210/materials-production-news/tech-firm-turns-to-robots-for-denim-effects.html
7. http://besttex-intl.com/wp-content/uploads/2019/10/vav-brochure-2019-min2.pdf
8. http://vavtechnology.com/robotics-technology/
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6 Sustainability Issues

This chapter is mainly a journal paper published in Textile & Leather Review journal, Croatia, 2021.

How to cite: Khan MKR, Jintun S. Sustainability Issues of Various Denim Washing Methods. Textile & Leather Review. 2021; 4(2):96-110. https://doi.org/10.31881/TLR.2021.01

Denim washing is increasingly joining the list of indispensable processes of meeting the demands of the world’s shifting fashion industry. Other than this, there is a rising trend in the sustainability perception among both producers and customers in the modern world. However, denim washing is considered to have direct impacts on the environment because of its chemical discharge and many other pollutants emitted during the process which affect water supplies. In the process, the denim industry encounters challenges at every level. Therefore, there is need for studying sustainable problems associated with denim washing. The unseen soul of the denim industry is technology, as nothing can be transformed without technological advancement. Sustainability problems of conventional washing have been addressed in this paper (i.e. pp spray washing, bleaching washing, stone washing, sand blasting etc.). Furthermore, the paper describes how sustainability can be achieved through the most recent washing techniques, such as laser, waterjet, nanobubble, ozone, NoStone, potassium permanganate alternatives etc. The introduction of new technologies has triggered a dramatic shift in the denim washing industry in terms of water usage, electricity and chemicals as well as improved quality. Consequently, it is undoubtful that the recent technologies in denim washing are crucial in making the industry sustainable. Moreover, the paper describes the idea of digitally printed denim and the available software for measuring sustainability in the process of denim washing.

6.1 Introduction

Overall, the textile industry, and specifically the denim industry, has always been a valuable industry, thus its extension expands its centrality in decades to come. Among all the existing textile products, no other kind of fabric has attracted such an acknowledgment as denim. Denim has been used extensively by different generations of people, sexual orientations and classes [1, 2]. On the basis of all-time fashion, denim may be considered a fabric and can be exceptionally a stylish fabric. For the sustainment during the fast-changing fashion, denim has undergone consistent advancement 3. There is a high developing denim demand from the youth, linked to reasons such as denim’s higher quality, strength, comfort level, low maintenance, and simple accessibility. Worldwide, the showcase of denim is expected to rise profusely in the coming years. Denim washing stands out as a part of the essential production processes needed to meet the rapidly rising and changing fashion market’s demands 2.

Brundtland (once known as the World Commission on Environment and Development) defines the buzzword, sustainability, as “improvement that meets the present desires without relinquishing future generations’ capacity” 4. Literally, sustainability refers to the act of preserving scarce and vital natural resources for future generations. Sustainability, in most manufacturing industries, is a primary motive. Sustainable practices explain the involvement beyond the customers and business, while the environment and community are essential 5. Currently, all are enthused to engage sustainability in the design and manufacturing processes in the continuously changing fashion trends 6. Sustainability can be identified through three components: environmental, social and financial sustainability. There is a close association between textiles and governance, social and environmental problems. However, the rising awareness of the social and environmental problems affecting the textile sector is the reason behind the increase in sustainability measures’ implementation over the past few years. The crucial consequences of sustainability in the textile industry pertain to denim manufacture as well. In the phase of manufacturing, sustainability is among the key challenges in the denim industry. In the industry, there exists a huge desire to ensure every phase of production is sustainable 7. However, during the selection of denim garments, customers are influenced by factors such as fashion, attractiveness, and aesthetics. Denim clothing, in the primary process, does not inherit the customer’s desired properties. However, it becomes effective after washing due to its new strength, comfort, softness, look and low cost, leading to the customer’s total satisfaction 8. Washing is considered an essence of finished denim and is the final stage of denim manufacture. However, different techniques of denim washing are employed to achieve denim’s fading effect, softness, as well as relaxed feeling [9, 10]. Besides, the industrial processes are linked to various environmental implications, mainly surrounding the heavy chemical usage and the extensive use of energy and water resources, effective wastewater treatment etc. Jeans or denim is also considered the world’s highest pollutant textile products, as a result of their indigo dying, the amount of water required to achieve excellent washes as well as chemicals used 11. In terms of achieving sustainability in the denim industry, every kind of washing technique has their own merits and demerits. In the past few years, various washing results have become prominent. Advanced materials, the latest technology and environment friendly washing techniques are establishing the sustainable production of denim. Therefore, a denim producer must be conscious, versatile, effective, and technologically aware of sustainability. Bangladesh’s denim industry’s future set-up will certainly affect the perception of modern technologies of washing. From this perspective, this study aims at expounding on the recent developments in sustainability achievement during denim washing.

6.2 Methods for Achieving Sustainability

The denim industry discharges vast quantities of wastewater into surrounding streams and bodies of water, thus leaving a large water footprint 2. With traditional washing recipes, every jean consumes 150 grams of chemicals, 70 litres of water and 1 kWh of power during the stage of denim washing [12, 13]. The old fashioned and time-consuming techniques are, therefore, not ideal for denim mass production and the manufacturing cost also increases 14. Because of the high costs of manufacturing resulting from energy, chemicals and water usage, an industrial-scale installation is viewed as a big concern for the achievement of a sustainable process. However, sustainability issues in denim washing may be categorized as follows:

i) Less water consumption for the blue planet.
ii) Elimination of wastewater.
iii) Reuse of water.
iv) Less chemicals for sustainable future.
v) Use of environmentally friendly chemicals and materials.
vi) Less energy for efficient manufacturing.
vii) The protection of human health.
viii) Shorter process.
ix) Process optimization in terms of time, temperatures and raw materials.
x) Quality improvement.
xi) Increasing productivity.
xii) Longevity of washing equipment.

Abbildung in dieser Leseprobe nicht enthalten

Figure 1. Significant parameters for sustainable denim washing 15

6.3 Sustainability Issues of Conventional Denim Washing

6.3.1 Sandblasting

Sandblasting treatment method washes the denim surface by using rough, high-speed impelling materials. Despite being banned in most countries, it is still employed in some parts of the world, mainly through radar, because it provides an inexpensive and simple technology of generating the anticipated effect on denim 16. Several brands, attempting to end the fatal method, prohibit the economically favored sandblasting. If sandblasting is carried out without adequate protective equipment, it can be extremely hazardous to employees’ health. The process produces vast quantities of silica dust that can be inhaled by workers, posing a great risk for a lethal pulmonary disease called silicosis. In an attempt to achieve a worn look, the use of brush or sandpaper strategy exposes workers to work-related asthma hazards because of the dust 17.

6.3.2 Stone Washing

For a long period of time, pumice stone has been used in the denim industry in creating an abrasion effect on the denim fabric. The denim style is characterized by a vintage, mildly distressed look. Despite several downsides attached to the use of stones, the abrasion effect remains the best solution. Stones, for instance, could subject denim to wear and tear, specifically on the waistbands and hems. In washing machines, everything is abraded, including the jeans’ rivets and metal buttons. Since the stones are disposed of, the process leads to the challenge of waste from the grit. By washing the denim repeatedly, the stones are supposed to be entirely removed 18. The use of pumice stones by machinery to abrade denim clothing is harmful. The crucial step of unloading the batch to remove stones incurs a time consuming, laborious process. To avoid stones remaining in the pockets, which can ruin the garments in later steps, the garment must be checked by the operator one by one. Dumping of waste stones is another environmental concern as it needs appropriate landfilling procedures. Stone inventories’ management needs are an additional burden for factories occupying valuable areas of land. Pumice stones are made up of fragments of ferrous and heavy metals that should eventually be separated from the garments with repeated washes 19. Material-based stone washing other than pumice stones leads to serious risks to the health of workers 17.

6.3.3 Bleaching Wash

The denim bleach strategy can be utilized in decolorizing indigo from denim, a process that involves a strong oxidative agent. The foremost commonly used chemicals utilized within the industry amid washing, with or without the expansion of stone include potassium permanganate, hydrogen peroxide, calcium hypochlorite, and sodium hypochlorite. The resulting decolorization is largely more apparent, depending on the treatment time, temperature and the intensity of the amount of the bleach liquor. The commonly used technique of denim bleaching is chlorine bleaching through sodium hypochlorite (NaOCl). Monitoring this process is difficult i.e. the same degree of bleaching may not be easily achieved in repeated runs 20. However, the release of hypochlorous acid and chlorine is environmentally harmful, as it threatens living organisms and harms the environment. Moreover, since it acidifies, it may cause pulmonary complications like the acute respiratory syndrome (ARDS), due to aspiration that may turn fatal. Despite its success in bleaching itself, it often produces an unpleasant scent in the resultant garment. Notably, sodium hypochlorite is an extreme irritant and can potentially impose substantial chemical burns on workers. After the bleaching process, the remaining hypochlorite should be expelled from the denim. Reducing agent treatment may be used in eliminating residual chlorine, also known as residual hypochlorite, and in a process called antichlor process. As a reducing agent, thiosulphate or sodium metabisulfite is used in denim. When mixed with water, it discharges a sharp and unpleasantly smelling gas and SO2-, which harms the ecosystem and spoils water 2. There is a common problem of yellowing, resulting from the residual chlorine from the process of washing in this case. Therefore, chlorine and manganese, which is a heavy metal, should be evaded for the sake of the environment. Traditional hypochlorite bleaching has been recognized to harm the stretch fibers and potentially leads to complaints 21. Hydrogen peroxide stands out as the cheapest method of bleaching. Also, during its storage, it has a high degree of whiteness and is difficult to be yellowed. However, it is disadvantageous in that, under alkaline conditions, high temperature bleaching requires energy efficiency improvement and may lead to substantial fibre damage 22.

6.3.4 Potassium Permanganate (PP) Spray Washing

Potassium permanganate (PP) is an oxidizing agent used for denim’s local bleaching and finishing. Besides, PP spray is used on jeans for lightening a particular area as well as creating whisker effects on denim. However, potassium permanganate (PP) spray is the most hazardous procedure for staff’s safety and health. When using a spray-gun to convert chemicals to micro-particles, workers performing this strategy absorb the micro particles, which cause lung problems, despite the implementation of various protective precautions 23. In this method, washing and neutralization consumes huge water volumes. Failure to effectively neutralize leads to yellowing. PP sprays have adverse impacts on laborers, as coming into contact with it bothers and burns the eyes and skin. Therefore, factory staff dealing with this chemical without safety equipment and proper ventilation systems may be at risk of long-term and short-term health problems 24.

6.3.5 Enzymatic Stoning Wash (Bio-stoning)

There has been a rise in the global awareness on enzyme use in textile processing aimed at minimizing pollution during textile production resulting from their eco-friendly and toxicity characteristics 25. For the enhancement of fabrics’ quality and comfort, enzymatic treatment is more effective than a variety of chemical and mechanical operations. The enzymatic stonewashing technique employing chemicals like cellulase is useful in the production of denim’s stonewash look. The invention of bio-stoning or enzymatic stonewashing entirely or partly replaced stonewashing. With the immense-looking market for distressed jeans’ garments, there is an increase in the use of enzymatic stonewashing. Bio-stone washing has increased the range of available finishes, opening up new opportunities of denim finishing. A small number of enzymes may replace large quantities of pumice stones 26. The enzymatic stonewashing increases the jean load by up to 50% as well as producing a softer finish and a perfect look [27, 28]. This technique improves both the clothing’s contrast and the abrasion effect. With partial or no use of stone, a fancy colour-fenced surface is produced. After the enzyme treatment, its rinsing process is lower than pumice stonewashing. Moreover, it has a lower stonewashing cost 29. Jeans stonewashed through this process have more durability. Besides, it ensures equal outcome under minimum volume, time, waste, water and machine damage. However, biostoning involves the release of water and chemicals into the effluent, thus the process is not friendly to the environment 30. Cellulase denim washing is highly precise and effective; with high resulting reproducibility, consistency, and fading effects’ precision, as in the case of productivity 31. While the outcomes in acidic cellulase are quicker, too much back staining decreases the indigo colour and affects the fabrics’ strength. The best stonewashing choice is the neutral cellulase due to lesser back staining, wider pH profile, and lesser strength loss than the acidic cellulase. It therefore lowers the need for rigid pH control producing a more reproducible wash-to-wash finish 27. Other cellulase applications in the textile industry include the bio-polishing of garments. Cellulase has the capability to hydrolyse microfibrils that protrude from the garments’ cotton surface. The microfibrils, after being damaged, appear to break away from the main body of the fibre leaving a smoother yarn’s surface 32. Besides the enzymatic treatment making the fibres’ surface “polished”, it decreases not only the fibres’ flexural rigidity, but also the strength of breaking due to the fibre structure’s degradation 33. Gokarneshan et al. suggested that, to achieve a desired effect, both stonewashing and biopolishing should be combined, which saves at least 30-50 litres of water per kilogram of denim garments 34.

6.4 Sustainability Issues of Latest Denim Washing

6.4.1 Enzymatic Wash

Enzymes have gained popularity as a substitute for chemicals used in shading/bleaching and are definitely advantageous in terms of wastewater treatment and the use of resources.

6.4.1.1 Laccases

Laccases are essential enzymes in the achievement of eco-friendly blue denim bleaching process. They are a part of the enzyme type of oxidoreductase. Generally, laccases do not work independently, but require a chemical mediator to be applied between the enzyme and the indigo. The enzyme is oxidized in the presence of an aqueous medium where it attacks the mediator and converts it to free radicals. Ultimately, the free radicals attack the indigo converting it into oxidized products 2. Moreover, the primarily used mediators are harmful. However, this enzyme’s benefit is the specific indigo dyes’ treatment and not in the fibre itself. The enzyme breaks down the indigo molecule without affecting other dyes like sulphur, direct or reactive dyes 35.

6.4.1.2 DeniLite® Cold

DeniLite® Cold is the new cold bleaching solution from Novozymes. The current method is based on enzymes named peroxidases, and operates without extra oxygen from either water or air. This new peroxidase has a high reaction speed, with 90% of the reaction ending in 10 minutes. Based on the gentle bleaching conditions, the cold bleaching technology enhances denim fabric longevity. The enzymatic conditions acting on the fabric’s indigo dye are tremendously precise. This ensures that the fabric’s elasticity and strength, unlike in tougher bleaching chemicals, remains unchanged 36.

6.4.2 Combined Washing Concept

Denim washing has substantially reshaped denim fashion’s sales demands and potential. Denim clothing industry’s significant breakthrough lies in the shades and results obtained, beginning from stonewashing to the recent enzyme washing processes and bio-polishing concepts 37. The rubbing of denim clothing pieces is done through a combination of pumice stones and enzymes, or the utilization of chemicals. Novozymes Denimax® Core, a recent wash processing plan from Novozymes, empowers the handling of the scrabbed area that goes on prior to the combined desizing process. While the conventional process has two rinses and two baths, the combined process has one rinse and one bath, reducing the water usage for more than 50%. As a result of reduced procedures, heat savings may be achieved by shifting from any of the conventional methods procedures to the combined process 38.

6.4.3 Nostone®+

NoStone®+, in conjunction with Levi Strauss & Co., is the newly revamped system of denim washing, developed by Tonello. The system is developed to overcome the environmental, mechanical, and economic constraints of stonewashing process. NoStone®+ framework’s premise is the stainless-steel rough drum, which is linked to the washing machine cylinder. The drum is handled in a special way to make it more or less abrasive, depending on the intensity of the desired effect or the needed treatment. The process’s nature is mechanical rather than chemical. The outcomes of NoStone®+ are similar to those of stonewashing, while also reducing the carbon footprint produced from the use of pumice stones. NoStone®+ also minimizes manual labour, preparing time, emissions, generation costs, and water usage. More so, it does not produce sludge nor dust, does not harm the system, and according to Tonello, it produces a uniform effect in both sampling and production 39. In conjunction to the NoStone® technology, enzymes may also be utilized in the accentuation of NoStone® process’s impact 24.

6.4.4 Potassium Permanganate Alternatives

Spray treatment with potassium permanganate is the most conventional and economical method 40. Despite being an effective technique, it has a high aquatic toxicity, thus imposing risks on health and the environment. Many countries have a duty or stringent rules to offer proof of preventing such misuse 41. Other developing chemical systems recently developed do not emit manganese into the atmosphere, as it is a heavy, non-biodegradable metal 24.

6.4.4.1 OrganIQ Product

The organIQ bleaching technique, a proprietary of CHT Group, is the first fully biodegradable and purely organic denim bleaching agent that achieves sustainable, remarkable results. Application of this technique does not require extra neutralization and does not pollute wastewater with hazardous contaminants, when properly used. Under a combination of organIQ bleaching agent and organIQ biopower, there will be no need to use chlorine, potassium permanganate, or stones. Moreover, the really fluffy products become perfectly smooth and develop a precious character 42. Modern techniques’ combination, such as organIQ + fog application, produces fully effective ecological washing results, and ensures resource protection 43.

6.4.4.2 Nearbleach Sky White

Nearbleach Sky White, designed for localized bleaching, is applied in brush and spray technique, in combination with hydrogen peroxide and the catalyst, Katalin Sky White, to achieve a controlled and quick bleaching for denim garments of high whiteness. In this process, time and water is saved. After application, there is need for only a simple washing step, with no neutralization 44. Acticell Technology Solution Acticell technology solution is designed to produce bleaching effects, just like potassium permanganate bleach. It also works best as an alternative product in achieving localized bleaching results (Acticell RT, Acticell B3). The desired outcome can also be achieved at any temperature, e.g. 60°C or room temperature. The bleaching effect takes place during a heating operation. The product has been certified by GOTS 45. Garmon Avol Oxy White Garmon Avol Oxy White is free from all drawbacks associated to potassium permanganate toxicology, including toxicity to aquatic creatures. Moreover, workers’ health is secured. It provides simple application, handling protection, and a stunning consistency. Tumble drying or curing must be avoided as it is inappropriate and results in tensile loss and cotton tearing 46. Peristal BLI Eco Alternatively, Peristal BLI Eco system is used instead of oxidative spray bleaching, which also ensures sustainability and effectiveness when dealing with denim jeans that are indigo-dyed. This method is effective as it does not contain any heavy metals nor chlorine, thus conforming to most environmental requirements, like bluesign® and ZDHC. Moreover, the products are odourless and free from alkylphenol, formaldehyde, ammonia, and heavy metals’ ethoxylates. Additionally, their oxidizing reactivity is very high. For the workers’ safety and security, there should be strict adherence to the crucial safety measures in the industry 47.

6.4.5 Ozone Washing

Ozone washing is an innovative waterless technology. The ozone imposes crucial effects on clothing as well as the environment [48. 49]. The ozone is a triatomic molecule with three oxygen atoms. One of the artificial methods of producing the ozone is corona discharge. The gas fades dyed textile fabrics by rupturing the chromophores of natural or synthetic fibres. Due to the high oxidation ability of the ozone (E=2.07 eV), it can easily decompose complex aromatic rings of dyes, resulting in decolorization. In order to generate ozone (a strong oxidant gas), only air and electric energy is used 11. On treated products, the ozone does not leave secondary derivative products, because it is chemically unstable. The garment may be bleached through this technique. During denim garment bleaching, the ozone is dissolved in the water in the washing machine. Moreover, denim garment bleaching and fading may be done via the use of the ozone gas in closed chambers. When compared to other oxidizing bleaching agents, the use of the ozone gas is much faster, as it only takes 15 minutes, while conventional bleaching takes 30-50 minutes 2. While the ozone finishing uses two to three washes and rinses, stonewashing or chemical bleaching uses six to seven. Despite the inability of the ozone to eliminate water use during jeans finishing, it greatly lowers water consumption. By decreasing the temperature needed and the amount of water that should be heated for wet finishing, it decreases energy consumption. Besides the reduction of chemical and water consumption from 85% to 95%, and energy from 70% to 80%, Jeanologia’s G2 Dynamic technology is designed to guarantee a detoxed and sustainable fabric. For instance, if 15 to 20 litres of water are required per kilogram of fabric, the whole process will only require 0.5 to 3 litres of water per kilogram with G2 Dynamic 50. G2 technology, by using ambient air, develops the garments “sun-washed” effect with the real look of outdoor use. In addition, using the ozone instead of some conventional finishing eliminates the effluent as well as the generation of sludge from the pumice stones. This technique is simple and friendly to the environment, because after laundering, the UV radiation may deozonize the ozonized water 18. Additionally, the ozone is applicable beyond shading, such as in stonewashing, to replicate other processes of denim finishing. This approach is sustainable due to its high quality, comparably better performance, long-lasting effects of the operation, low maintenance costs, simple installation, minimal bleaching production costs, and high production capacity and efficiency. Nonetheless, safety procedures and features should be key in the avoidance of workers’ deadly or dangerous accidental exposure to the ozone gas. Since it runs in dry conditions, the system enhances whiteness and eradicates the jeans pockets’ back staining as well as other potential organic spots 51.

6.4.6 Nanobubble e-Flow Technology

Nanobubble e-Flow technology can handle raw clothing and apply different chemicals, move the clothing with the use of micro-nanobubbles (MNB) as the chemical product vehicle capable of directly getting inside the fibres 52. The process involves injection of atmospheric air into the electro-flow reactor and then subjecting it to an electromechanical shock to generate wet air flow and nanobubbles 53. Different chemical products such as dyes, antimicrobials, liquid repellents, wrinkle-free resins, softeners etc. are used to pass functional properties to the denim. Through the application of this modern technology, the revolutionary feature is that certain items get into contact with garments with minimum water amount 54. The nanobubbles’ skin has a duty to transport the chemicals to the garments 12. Water and chemicals are homogeneously blended with the help of microbubbles and spread on the garment 55. Nanobubble technology boasts of significant success such as 86% water use reduction, 97% wastewater reduction, extremely low liquor ratio of 1:1, the recycling of steam/water, energy use reduction up to 80%, 50% chemical products saving, related chemical wastage reduction, reduction of the washing and drying process, as well as necessary temperature reduction and reduction in CO2 emissions [54,56]. The method is, therefore, cost effective. It can create a washed look by laser as well as the wet ozone process creates a bleached look over the denim 56. The e-Flow process provides pre-shrinkage of the fabric, thus avoiding high shrinkage during washing at home. Moreover, it improves the colour fastness to rubbing properties 53. If the surface of the fabric is meant to achieve a stonewashed effect by enduring a high degree of abrasion, the e-Flow technology, on the basis of aesthetics and sustainability, is a commercially viable choice. However, it is important to consider the productivity factor. Chemical suppliers have produced cellulase enzymes usable in e-Flow, such as the DyStar’s Lava® Cell NEF 57.

6.4.7 Water Jet Fading

Conventionally, the jeans’ abrasion and whitening processes are done either with manual brushing or permanganate sprays, whereby the two techniques are harmful to the respiratory system, skin and the eyes. By using water during whitening, Tonello’s Water Brush tackles the above disadvantages 58. Hydro jet treatment often needs hydro jet nozzles’ contact to the one or both surfaces of fabric. There is much relationship between the degree of colour washout, pattern clarity, resulting fabric softness and the nature of the dye in the fabric and the manner and degree of fluid impact energy added to the fabric. Blue indigo dyed denim produces exceptionally essential outcomes 18. Fascinatingly, Tonello’s water brush uses water, but does not absorb it. The water used in garment whitening is gathered by a large tank under the spray robot. The tank filters the water then recycles it back to the robot. Again, the highlights include its zero influence on the workers and the ecosystem, and the reduction of resource use 58. Tonello has an aim of replacing the manual and permanganate brushing techniques with highly pressurized water through Water Brush incorporation in finishing processes to create the same worn effect without applying heavy chemicals. The chemicals not only pollute the environment but also pose risks to the workers involved in the process.

6.4.8 Laser Technology

To avoid some of the shortcomings of the traditional technologies, a new revolutionary approach has been established under laser technology’s advent in the textile industry 59. It is another sustainable option in the denim washing field. This is the fastest growing and approved technology of the denim industry, and has made denims go green 13. Laser finishing is referred to as denim spray painting. Lasers are employed during laser engraving as well as laser marking. The method is often used to replace environmentally disadvantageous and potentially hazardous typical dry techniques, such as grinding, destroying, hand sanding, sand blasting etc. 59. Via this technique, the dye on the surface is decomposed by the laser beam and the subsequent components are converted to vapour and expelled away. The efficiency of fading is dependent on the wavelength of the laser beam, pulse duration and power density 3. Laser technology provides infinite exploration and innovation possibilities for designers. This technique creates patterns carried out by computer-managed processes, such as even images, text, lines and dots 13. Therefore, it can be used in creating personalized patterns and designs or generating worn-out effects like rips, abrasions and whiskers. It is also capable of providing detailed duplicability of the applied results. Moreover, laser engraving is useful in fabrics’ burning and colour fading to generate embroidered designs in the cloth. Lasers are preferred for low-cost sealed CO2 and laser engraving 60. There is a possibility of pre-programming the laser with designs that may exactly replicate the anticipated look obtained through manual sandblasting and sanding with considerably minimal labour and physical hazards. To produce a variety of denim looks, it requires less water, chemicals and electricity. For an enhanced laser effect to mimic heavier bleaching applications, an addition of laser boosters to the fabric may be effective 24. Furthermore, it reduces production costs and saves time. According to experts, these technologies have led to 500% production increase per workplace and 50% fabric strength loss 13. Moreover, the software, such as E-Mark and CarbonLaze, increases industrial efficiency, gives room for more innovation, simplifies design, and decreases steps of pre-production process. In conjunction to an eco-washing system, laser technology for finishing jeans has led to outstanding environmental benefits. This new technology saves 85% of chemical products, 67% of water, and 62% of electricity 13. The most complex issue associated to laser processes is the inaccuracy of the laser beam magnitude. When low, it is difficult to obtain the effect, and on high laser strength, it may destroy the fibre bonds, leading to tearing and chemical damage 1. Furthermore, the fading process is linked to a high eye damage potential 3. It was hard to operate and maintain the early laser systems. However, the current laser systems are easier in terms of service and maintenance 60.

6.4.9 Plasma Treatment

With a wide range of sustainable technologies, many would consider the plasma treatment as an effective way of replacing traditional chemical processes, because it facilitates the achievement of the desired outcome using an appropriate reactive gas, and it is a dry process as well. Avoiding chemical waste is the key attraction of plasma in industrial operations. Saving vast amounts of water, chemicals and electricity is another benefit 61. The plasma is an incompletely ionized gas, and is often referred to as the fourth state of matter. Upon the exposure of a substance to the plasma, a number of plasma particles (neutrals, radicals, ions, and electrons), as well as UV photons reaching the surface with various energies’ distribution, bombard the surface. A number of these active species are energetic enough to detach chemical bonds and prompt fibre surface reactions 62. The RF and Corona’s low-pressure treatments resulted in an improvement in denim lightness, implying elimination of indigo dye from the fabric surface. To achieve a worn look for indigo-dyed denim fabric, corona treatments and low-pressure plasma may serve as a viable alternative to the traditional bio-stoning. However, further research is required in order to prevent harsh fabric handle emergence and the upsurge of yellowness 63.

6.5 Sustainability Issues of Digitally Printed Denim

On its sustainability journey, the textile industry is gradually inclining towards digitalization 64. Digitally printed denim uses a mechanism that can bring denim to a new level, by using textile inkjet printing as an artistic method 65. Digital printing can create precise image data, with the use of millions of colours in infinite motif format. Under this technology, it is possible to create visually convincing design specifics that mimic the real thing, like abrasion areas, whiskers, and yarn slubs 66. Digi Denim is a completely ‘waterless’ kind of denim. Among the traditional washing processes are pre-treatments, enzyme washing, bleaching, and neutralizing. Every step in this process requires a significant amount of water. The digitization of denim industry contributes to sustainable practices. Without any natural resource or material waste, digital design can create countless pairs of jeans, thus lowering waste levels and the environmental impact. Digi Denim provides a huge cost decrease and the overall lead time. It is a sustainable and cost-effective option as opposed to the traditional denim finishing and colouring techniques 1.

6.6 Software for Measuring Sustainability in Washing

The control of the cost of energy, chemicals, and water in the production process is aimed at developing an ethical, productive and environmentally friendly denim washing system. Through the evaluation of the current impacts, the defining interventions and areas of change are easily recognizable, and can thus be tracked for sustainability.

6.6.1 Environmental Impact Measuring (EIM) Software

EIM software is used in the assessment of the environmental impact of finishing processes for garments in categories such as: the use of water, the use of energy, the use of chemical products and health of the workers. With regard to water, a low-impact process is defined by the EIM as consuming less than 35 litres of water per garment. The EIM takes a product’s toxicology into consideration. It penalizes the use of more chemicals for contaminants, regardless of the amount of the substance used. The environmental effect of a complete finishing process can also be calculated by the EIM. The individual can clearly see the key cause of the environmental hazards with this tool, giving them the requisite data to move towards a more environmentally friendly process. The EIM also enables the consumer to compare various processes and determine their resulting outcomes in terms of sustainability issues 67.

6.6.2 Environmental Score (eScore) Software

VAV Technology developed the eScore Software for denim manufacturing industries that calculate and compare the quantities of chemical, electricity, and energy reference values, as consumed by the machines based on the prescriptions. It provides data on the lower and upper limits to protect the environmental and human health, data on the system effort and utilization of ability. Based on each company’s water and chemical consumption, eScore Software ranks the companies and categorizes their scores as follows: i) 0-33 Score: Environment-Friendly Production, ii) 33-66 Score: Acceptable Production, iii) 66-99 Score: Limit Value, iv) 100 and more: Non-Environment-Friendly Production 68.

6.7 Conclusion

Different kinds of mechanical or dry-washing processes and chemical or wet-washing processes create a lucrative outlook for the denim washing system. Relating to sustainability concerns, the traditional washing methods are linked to tremendous health and environmental risks. However, with new technologies and approaches to denim washing, sustainable and attainable solutions are currently available, capable of supporting the environment, the consumer and the company. Following the denim industries’ adoption of new technologies in the manufacturing process, there has been a drastic decrease in the use of energy, chemicals and water during the washing of denim fabrics. It is worth stating that these new technologies, including waterjet, ozone, and laser technologies, have presented themselves as excellent options for denim washing regarding the expense, time, durability, consistency, and efficiency. As a result, the denim industry will soon experience dramatic changes following the new developments. However, there is need for further advancement in denim washing techniques to enhance sustainability of the industry.

6.8 References

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7. Testing Principles of Washed Denim

Md. Khalilur Rahman Khan, Hosne Ara Begum

Testing is an integral part of the textile business which is primarily employed during the production process as well as for the quality certification of any final product. Therefore, knowing the testing principles for denim items is also significant. In fact, various testing principles are employed to check the different types of quality parameters of denim garments. In this chapter, it is attempted to briefly describe the principles of prominent testing used for assessing the quality aspects of washed denim. Besides, the primary information associated with various types of quality parameters of denim items is also briefly mentioned in this chapter.

7.1 Significance of Washed Denim Testing

Quality control plays a very vital role for any kind of business, any company, or industry, particularly for the textile business. In fact, it is an important aspect of the product development and production process in order to create and maintain high-quality denim cloth. High quality denim simply means high performance in terms of required quality parameters, which must be confirmed by quality tests. The comfort of denim textiles as well as the physical, chemical, and mechanical aspects of the cloth determines their quality. As the demand for denim escalates, we must maintain that the quality of denim meets consumer expectations. However, quality tests are necessary not only to ensure the product's promised features, but also to assess complaints from customers and demands. By testing, an analysis of whether the reclaims are true or not can be done by examining the denim items.

Denim quality is affected by both the material and the manufacturing process. In today's denim value chain, the washing process is quite crucial. Denim washings that offer it a faded and worn appearance affect not only its durability but also its ability to retain its qualities 1. As a result, concerned people need to be educated on how to ensure high quality denim garments after employing different types of washing methods. By being careful during washing, producers can ensure high quality denim items, which require testing the washed denim through established methods.

Various types of testing procedures are employed in order to analyze the effects of different types of washing processes on denim properties such as strength, color change, drape, stiffness, and so on. Lists of washed denim quality parameters, which are generally needed to be tested, are given below:

- Tear strength
- Tensile strength
- Dimension stability
- pH value
- Color fastness to washing
- Color fastness to rubbing
- Color Fastness to light
- Color Fastness to water & sea water
- Colorfastness to dry-cleaning
- Colorfastness to perspiration
- Pilling resistance
- Abrasion resistance
- Drape ability
- Air permeability
- Fabric stiffness
- Phenolic yellowing
- Appearance after wash

7.2 Tear Strength

Tear strength is the fabric's resistance to tearing or the force necessary to propagate a tear after it has commenced. The force needed to propagate an already tear, not the force required to generate a tear, is the fabric tear parameter which is assessed. Tearing strength is characterized as the force necessary to keep tearing a cloth in either the weft or warp direction under specific conditions. It is perhaps the most common type of fabric strength failure. It's especially significant in fabrics that are subjected to a lot of wear and tear. Textiles with high tear strength ensure that punctures in the fabric do not spread quickly.

7.2.1 Dynamic Tear Test

A dynamic tear method has an application for clothing fabrics, such as cotton fabrics destined for jeans. The tear properties of fabrics may be measured using the ballistic pendulum method (Elmendorf) according to NF EN ISO 13937-1 (2000). The principle of this method is explained in the standard: the force required to continue a slit previously cut in a fabric is determined by measuring the work done in tearing the fabric through a fixed distance. The main element of the device for dynamic tear strength is a ballistic pendulum (shown in figure-7.1), by means of which force is suddenly applied to the appropriately prepared sample. The sample is then mounted between two jaws, one fixed and the second, movable one mounted to the device’s body. A sharp knife is situated between the two jaws to begin the tear of the test specimen by cutting a slit of 20±0.5mm, and the tear distance is 43±0.5 mm. A pendulum carrying moving jaw, which is in alignment with a fixed clamp when the pendulum is in the raised, starting position with maximum potential energy. The pendulum is then released, and the movable jaw, which is connected to a pendulum, falls down due to the gravimetric force, and the specimen is torn completely as the moving jaw moves away from the fixed one. The tear force is measured by using the principle of conversation of energy, which measures the energy consumed to test the tearing of a specific length of fabric. The advantage of the dynamic tear test is the option of quickly obtaining the results of the tear test (from readings directly on the device) [2,3].

Abbildung in dieser Leseprobe nicht enthalten

Figure-7.1. Elmendorf pendulum testing machine 4.

7.3 Tensile Strength

The tensile test is one of the most basic mechanical tests that can be conducted on a material. The tensile strength of denim is a significant characteristic, and testing is usually done separately on the warp and weft 5. In its most basic form, tensile strength refers to a material's capacity to endure a pulling (tensile) force. When a yarn or fabric is subjected to uniaxial tensile loading, its tensile strength is defined as the highest load it can withstand without breaking.

7.3.1 Grab Test

To quantify the tensile strength of a piece of fabric, grab test method is often used. ISO 13934-2:2014 (grab test) or ASTM D5034 specifies a procedure for the determination of the maximum force of textile fabrics. The testing condition is closer to the load application on a fabric in practical use. This method is used to determine the effective breaking strength and elongation of woven, non-woven and felted fabrics using the principle of constant rate of extension. This test method is not recommended for glass fabrics, knitted fabrics and other textile fabrics having more than 11% elongation. There are two types of test methods to identify the grab strength. They are i. Grab test ii. Modified grab test. These two testing methods are alike, but smaller changes are required in sample preparation 6. The grab test (shown in figure-7.2) and the modified grab test are considered satisfactory for acceptance testing of commercial shipments for most woven textile fabrics.

Abbildung in dieser Leseprobe nicht enthalten

Figure-7.2. Clamping principle in Grab Test.

A grab test is a tensile test in which the center part of the specimen width is gripped in the tensile grip jaws. Due to the way the sample is gripped, edge effects, which may cause inaccurate data for fabrics, are eliminated. Tensile force is applied to the fabric specimen until rupture and maximum force is recorded. A fabric sample (100 mm x 150 mm) is extended in a direction parallel to the direction of warp or weft. The clamping area ((25±1)×(25±1)mm2 ) is smaller than the specimen width, which is 100±2mm. The initial distance between the clamps (gauge length) should be 75 mm and speed (e.g., 300 ± 10 mm/min) is adjusted so that the sample is broken in 20±3s. A minimum of 5 specimens per direction are tested. No pretension is applied when the sample is secured in the clamps. This test method provides the maximum force.

7.4 Dimensional Stability

The ability of a textile to withstand changes in its dimensions is referred to as dimensional stability. Under the conditions of washing, drying, steaming, and pressing, a fabric or garment may shrink in certain dimensions while growing in others 7. Fabric dimensional stability is governed by factors such as fiber moisture absorption, yarn tightness, and fabric structure. Fabric dimensional stability is also influenced by the fabric's processing tension. If the processing tension increases, the fiber deformation increases, the internal stress and the slow elastic deformation increase, then the relaxation and retraction degree of the fabric increases after soaking, which make the shrinkage rate of the fabric increases obviously. Furthermore, temperature has a significant impact on fabric shrinkage, as high temperatures cause relaxation and expansion, as well as heat shrinkage. The dimensional stability of fabrics is affected by their raw materials. The dimensional stability of the fabric also varies due to weaving, dyeing, and finishing methods.

7.4.1 Dimensional Stability Testing

Dimensional stability will be measure the shrinkage % of before and after wash samples. Through industry-driven standards developed under organizations like the American Association of Textile Chemists and Coloration (AATCC) and the International Standards Organization (ISO), specific dimensional stability tests have been created to assess how garments and fabrics behave under conditions fine-tuned to emulate typical consumer practices. Various tests are carried out here, including EPI and PPI count measurement, GSM measurement, shrinkage test, and twisting test.

7.4.1.1 Dimensional Stability to Washing

The material is conditioned under standard climate (i.e., 20°C & 65 ±2%). Following steps are employed for this test 8:

a) AATCC Washing

i) Machine: Top loading washing m/c
ii) Ballast: 920 mm x 920 mm hemmed pieces of bleached cotton (type 1) or 50/50 polyester/cotton bleached and mercerized poplin (type 2) or 50/50 polyester/cotton plain weave (type 3)
iii) Total load in washing: Preferably specimen + ballast should weigh 1.8 ± 0.1 kg.
iv) Detergent: 1993 AATCC Standard Reference Detergent in amount 66 ± 1 g for m/c wash.

b) ISO Washing

i) Machine: Preferably front loading m/c
ii) Ballast: 100% knitted polyester texturized filament fabric having a mass per unit area of 310±20 g/m2. Four pieces of size 20 x 20 cm, overlocked together on all four sides or 100 % bleached cotton fabric or 50/50 polyester/cotton plain-woven fabric of mass per unit area 155±5 g/m2 and of size 92 x 92 cm.
iii) Total load in washing: Preferably specimen + ballast should weigh 1.8 ± 0.1 kg.
iv) Detergent: ECE or IEC ref detergent + Sodium perborate tetrahydrate + bleach activator TAED in 77:20:3 ratios.

c) Testing Procedure

i) Mark the dimension on the piece of fabric or garment before washing with a textile marker. The markings on a piece of fabric are done with a standard template (38×38 cm2 or 50×50 cm2).
ii) After the wash, measure the reduction in that dimension with a scale
iii) The change in dimensions or shrinkage is reported in percentage.

Calculation: Shrinkage % = (Dimensions before wash – Dimensions after wash)/ (Dimensions before wash).

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Figure-7.3. Skewness after denim wash.

7.4.1.2 Distortion or Skewness after Wash (Torqueing)

Spirality is the twisting of fabric in a garment after it has been washed. This term is also used interchangeably as torque or skewness. The origin of spirality is from fibre, yarn and fabric construction. When a fibre is distorted, its molecules tend to return to the manner it was produced or made. This is known as the ‘memory effect,' and it is the most common cause of spirality 9. Twisting jeans (shown in figure-7.3) is a problem for jeans manufacturers. The skewness after wash test is used to determine the potential of yarns shifting or distorting in a fabric. Because of the resulting changes in appearance, such distortions are unacceptable. The AATCC 179 method is applied in this test. The following are the testing principles: i) Before washing, denim clothing specimens are marked. ii) After two standard laundering cycles, the alignment of the marks is checked. iii) The percent skew is determined, and the skew direction is noted. The calculations in this method do not create negative skew values; hence a value near to 0 indicates greater skew. Seam torque should be less than 5% of side seam length, and skewing should be no more than 3% of cloth width. Following formulae are used:

i) Spirality % = [(shift in side seam)/ (side seam length)]* 100
ii) Skew % = [(Displacement/ Fabric Width)] x100.

7.5 Color Fastness

Colour fastness of textiles is an important criterion for judging the quality of dyed and printed fabrics. Color fastness refers to a material's resistance to changes in any of its color properties, as well as the transfer of its colorants to adjacent materials. Color fastness is determined by fiber quality, fabric construction, dye type, shade depth, color, and dyeing process parameters. Washing fastness, light fastness, rubbing fastness, perspiration fastness, chlorine fastness, ironing fastness, and so on are all examples of color fastness. Color fastness testing of fabrics can be done using a variety of standard test methods.

7.5.1 Color Fastness to Wash Test

This technique is used to determine how resistant the dyed fabric's color is to various types of washing in water with soap and detergent. The BS EN ISO 105-C06:2010 for color fastness (Part C06: color fastness to domestic and commercial washing) and the AATCC test method 61-2003 are also frequently used.

According to BS EN ISO 105-C06:2010, dyed fabric having dimensions of at least 10 cm × 4 cm are sewn together with standard multi-fiber strip. 4 g of detergent per liter of water is used to make a washing solution. The sample is washed in a washing machine at a speed of 40 revolutions per minute using one of the sets of conditions. Different liquor volume, washing temperature, chlorine level, perborate level, steel ball quantity, and pH are employed in these tests. In fact, abrasive action on the dyed fabric is obtained by using a high number of steel balls and a low liquid level. The gray scale ratings for color change and staining can be calculated using the appropriate gray scales.

7.5.2 Color Fastness to Rubbing (Crocking) Testing

The proportion of color moved from the dyed sample to the white fabric under specified rubbing circumstances is revealed in this test. It is carried out with the aid of crock metering equipment (shown in figure-7.4), which can be handled manually or electrically. With the BS EN ISO-105-X12 test method, dyed fabric dimensions should not be less than 50 mm × 140 mm. A dyed fabric sample is secured to the crock meter's base, while a 5 cm x 5 cm piece of white bleached fabric is attached on the finger of crock meter and rubbed against the dyed fabric. The finger is rubbed against the dyed fabric at the speed of one turn per second (10 × 10 s). Then the white finger cloth is removed and a gray scale evaluation is performed. On a scale of 1–5, a rating is assigned. Except for the fact that the finger cloth is wet before rubbing, the process for wet rubbing fastness is identical to that for dry rubbing fastness. It is very critical to keep the pick-up of the fabric at 65%, otherwise significant variations can be observed.

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Figure-7.4. Crock meter [image Courtesy: Haida International].

7.5.3 Color Fastness to Perspiration Testing

The perspiration generated by human body is a complex chemical that contains a high number of salts. It can be acidic or alkaline based on the human metabolism. Color fastness to perspiration tests are conducted using a solution created by imitating acid and alkaline perspiration. At the moment, the ISO 105 E04, AATCC 15, and JIS L 0848 color fastness to perspiration test methods are commonly used.

Two specimens (100 mm x 40 mm) are cut along the fabric's length or width. To make a composite specimen, the test specimen and multi-fiber fabric are aligned and sewn together at the short edge. Samples are dipped in a solution typically made up of histidine before being tested. To confirm that the specimens are thoroughly soaked, one composite specimen is immersed in alkaline solution and the other in acid solution for 30 minutes at room temperature. The perspirometer's upper pressure plate is lowered to the top of the acrylic plates, the loading weight is put on the pressure plate, and the side screws are adjusted. This corresponds to a pressure of 12.5 kpa (5 kg) being applied to the specimens in between. The perspirometer is put in the oven and heated to 37±2o C degrees Celsius for 4 hours. The sample is then dried individually. The gray scale is used to determine a rating from 1 to 5.

7.5.4 Color Fastness to Light Testing

This test is used to assess color fading when the sample is kept under a specific light source. The test samples are exposed to light for a specific amount of time (24, 36, 48, 72 hours, etc.) or in response to customer demand, under specific lighting, temperature, and humidity conditions, and then compared to reference samples. The color change is measured using a blue scale. Due to the end-use performance expectations, many items such as carpets, curtains, and upholstery require excellent light fastness. Samples are subjected to an intense artificial light supplied by a Xenon arc lamp to assess light fastness. The light moves through a succession of filters to guarantee that its wavelength (spectrum) closely matches that of natural daylight passing through the glass. The test environment's humidity and temperature are both controlled. A small sample of material is subjected to high light alongside a set of eight blue wool standard cloths (reference 1–8). To see whether fading develops steadily or at a different rate than the longer-term exposure, two exposure times are employed. The number of the blue wool standard that indicates the equal degree of color change is used to establish a light fastness rating to each sample.

7.5.5 Phenolic Yellowing Testing

For many years, the textile industry has struggled with yellowing of white and pastel-colored textiles and apparel. The majority of yellowing issues are caused by the migration of phenolic antioxidants from packing materials onto textile substrates, resulting in the yellowing phenomena. Phenolic yellowing is a yellowing of textile materials induced by phenolic chemicals in the presence of nitrogen oxides (NOx).

ISO 105-X18:2007 provides a method for determining the potential for phenolic yellowing in textiles. The approach is only applicable to phenolic yellowing and does not address any other sources of yellow discoloration on textiles. This test should be done on cloth that hasn't yellowed. A test package is prepared, consisting of test papers, test specimens (3 cm x 10 cm) and one control fabric. Each specimen and control fabric are individually positioned in a horizontal arrangement between a folded test paper and two glass plates (i.e., acrelic-resin). To make an airtight package, the stack of plates, test papers, specimens, and control fabric is wrapped strongly in BHT (butyl hydroxytoluene) free polyethylene film. The package is put (at 12 Kpa) into a test device (perspirometer), which is then placed in an incubator/oven for a set amount of time (e.g., 16 hours) at a specified temperature (503°C). Eventually, the package is removed and left to cool before being unwrapped.

Test specimens should be evaluated within 30 minutes of unwrapping. It's crucial to ensure that the control fabric has been yellowed to a grade 3 on the grey scale. If not, the test was not successfully completed and must be repeated. With the use of a grey scale, the amount of yellow color staining for the sample under the D65 light source is determined.

Table-7.1. Minimum performance standards for denim 9.

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7.6 Determination of pH Value

In the denim production line, pH measurement is critical. The acid and alkaline components of the fabric residue are one of the few signs of dangerous compounds influencing human health, and the pH value of textiles refers to them. The pH of textile products for children and direct skin exposure should be kept between 4 and 8.5. Textiles with a high pH value will disrupt the skin's weakly acidic environment on the human body's surface, causing irritation and exposing the skin to other pathogenic bacteria, as well as dermatitis and other symptoms. Furthermore, the fabric's high or low pH value makes it very easy to degrade the fabric during storage. Table 7.1 shows the minimum performance standards for denim.

In ISO 3071, the pH test is performed as follows: All receiving samples must be kept in a temperature of 20±2 °C & humidity of 65±2 °C for at least 4 hours. Then, from three different positions of denim cloth, exact 2.0 0.1 gms of fabric are taken. The sample is cut into small pieces, and the maximum size should be 0.5mm. Firstly, the pH of distilled water is determined and recorded. Furthermore, if the client is instructed to use potassium chloride (KCl), the customer must add 0.1N KCl and make the solution. The specimen is then immersed in a 100ml solution and placed in the conical flask. It is therefore allowed to shake for two hours at 30 rpm with a rotary shaker. After that, the pH rod is properly washed, and the pH is measured in three different extracted solutions.

7.7 Light Sensitive Fabric (LSF) Test

Jeanologia, a provider of sustainable denim washing technologies, unveiled their new light sensitive fabric (LSF) test. The LSF test creates a study that examines the fabric's response to sustainable methods, primarily laser, in order to obtain the desired look and washes while consuming less water, chemicals, and energy. With Jeanologia's Light Solutions, the LSF tool (shown in figure-7.5) classifies the fabric based on its laser reaction, assessing the grey scale, the efficiency in imitating natural tears, and the visual development. It is feasible to significantly reduce the environmental footprint of washing procedures with this technology 10. The light sensitive fabric test affirms the highest laser intensity capability while also lowering product development time and effort.

Bluescan is a high-tech testing cabinet that uses the Light Sensitive Fabric Test (LSF test) to determine how fabrics react to laser technologies. It generates very exact data, allowing users to choose the ideal cloth for their applications. Bluescan uses a laser illuminant to scan a specific area of the fabric and capture the scattering reflexion in order to analyze the data. Bluescan generates a comprehensive report with accurate and clear information within minutes after the experiment is finished. This report aids in determining if the cloth under investigation is suitable for sustainable washing 11.

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Figure-7.5. Denim fabric showing the new Light Sensitive Fabric (LSF) test (c) 2017 Jeanologia 12 [Image courtesy: https://www.texdata.com/news/Sustainability/10668.html]

7.8 Appearance Test after Wash

This test is used to assess the appearance of denim items after they have been washed. The appearance of the specimen is rated in comparison to other reference specimens under standard lighting and viewing conditions. Denim washing causes seam collapse, such as insufficient seams, partial or non-inclusion, shape distortion, shade change, and so on.

7.9 References

1. Sakib N, Zhu G. (2019), Experimental Investigation to Evaluate Critical Aspects of Denim Quality, IOSR Journal of Polymer and Textile Engineering, Vol-6(2):50-55.
2. Witkowska, B., & Frydrych, I. (2004). A Comparative Analysis of Tear Strength Methods. Fibres & Textiles in Eastern Europe. April / June 2004, Vol. 12, No. 2 (46).
3. Dolez p., Vermeersch O., Izquierdo Izquierdo V. Advanced Characterization and Testing of Textiles, Chapter-2: Advanced strength testing of textiles, Pp-44. © 2018 Elsevier Ltd.
4. Retrieved from https://www.testerinlab.com/news/217.html
5. Nasrin Akter, Md. Reazuddin Repon, Daiva Mikučionienė, Mohammad Abdul Jalil, Tarikul Islam, Md. Rezaul Karim, Fabrication and characterization of stretchable denim fabric using core spun yarn, Heliyon, Volume 7 (12), 2021, https://doi.org/10.1016/j.heliyon.2021.e08532.
6. K. Amutha, A Practical Guide to Textile Testing, chapter-4: Fabric Testing, © 2016 by Woodhead Publishing India Pvt. Ltd.
7. Değirmenci, Züleyha & Celik, Nihat. (2014). An investigation on the influence of laundering on the dimensional stability of the denim-like knitted fabrics. Tekstil ve Konfeksiyon. 24. 363-370.
8. Dipanwita Ray, Garment Testing - Home Laundering Methods, January 30, 2020, Online Clothing Study. Retrieved from https://www.onlineclothingstudy.com/2020/01/garment-testing-home-laundering-methods.html
9. Dr Subrata Das, Quality Characterisation of Apparel, © Woodhead Publishing India (P) Ltd., 2009, Pp. 24-26.
10. Jeanologia: light sensitive fabric test, Sep 9, 2017. Retrieved from https://textination.de/en/jeanologia-light-sensitive-fabric-test
11. Measurement technology for fabric – Bluescan, Retrieved from https://www.jeanologia.com/bluescan/
12. https://www.texdata.com/news/Sustainability/10668.html

[...]

• Auteur: Md Khalilur Rahman Khan (Auteur)
• Année de publication: 2021
• Pages: 167
• N° de catalogue: V1152706
• ISBN (PDF): 9783346566126
• ISBN (Livre): 9783346566133
• Langue: anglais
• mots-clé: denim, washing, terminologies, technologies, sustainability, issues