NEW ERA OF INDIGO YARN DYEING - NO BARRE ON KNITTING

Knit denim is a type of fabric that combines the comfort and flexibility of knitwear with the look of traditional woven denim. The yarn dyeing process for knit denim is crucial in achieving its unique appearance and texture. Here’s an overview of the yarn dyeing process for knit denim:

• Selection of Yarn: Choose the type of yarn suitable for knit denim, typically a blend of cotton and elastane or polyester for stretchability.
• Pre-treatment: Clean the yarn to remove any impurities or natural oils. This step usually involves scouring and bleaching to prepare the yarn for dyeing.
• Indigo Dyeing:

Indigo Preparation: Indigo dye is prepared by reducing it in an alkaline solution to form leuco-indigo, which is water-soluble and can penetrate the yarn fibers.

Dyeing Process: The yarn is repeatedly dipped in the indigo dye bath and then exposed to air (oxidation). This process, known as "dipping and skying," can be repeated several times to achieve the desired shade of indigo. Each dip and oxidation cycle builds up the color.

• Sulfur Dyeing (Optional): For deeper shades or to achieve different color effects, sulfur dyes can be used in conjunction with indigo. The sulfur dyeing process is similar to indigo dyeing but provides different hues and depths of color.
• Ring Dyeing Effect: To achieve the classic denim look with white cores and indigo surfaces, the dyeing process is controlled to prevent complete penetration of the dye into the yarn core. This results in a ring-dyed effect, which is characteristic of traditional denim.
• Post-Dyeing Treatment:

Washing: After dyeing, the yarn is thoroughly washed to remove any excess dye and chemicals.

Softening: The yarn is treated with softeners to enhance its feel and flexibility.

Drying: The yarn is dried to a stable moisture content, making it ready for the next stages of fabric production.

• Knitting: The dyed yarn is then knitted into fabric using circular or flat knitting machines, depending on the desired fabric structure and weight.
• Finishing: The knitted denim fabric undergoes finishing processes such as sanforizing (pre-shrinking), brushing, or washing to achieve the desired texture and hand feel.

Indigo acid wash is a technique used to give denim a distinctive, vintage look with high contrast patterns. This process was particularly popular in the 1980s and remains a sought-after style for distressed and retro-looking denim garments. Here's a step-by-step overview of the indigo acid wash process:

• Selection of Denim: Choose the denim fabric or garment that you want to acid wash. This fabric is usually dyed with indigo for the classic denim appearance.
• Preparation:

Protective Gear: Workers should wear protective gear such as gloves, goggles, and aprons to handle the chemicals safely.

Preparation of Garments: The denim garments are prepared by tying them with strings or rubber bands to create random patterns. Alternatively, the fabric can be scrunched or twisted.

• Acid Treatment:

Chemical Solution: A solution containing pumice stones soaked in a solution of potassium permanganate or other acid substances is prepared. Potassium permanganate is commonly used due to its strong oxidizing properties.

Treatment Process: The garments are tumbled with the pumice stones and the acid solution in industrial washing machines. The stones, combined with the acid, abrade the fabric surface, creating irregular patterns and removing some of the indigo dye.

• Neutralization:

After achieving the desired acid wash effect, the garments are removed from the washing machines and thoroughly rinsed to remove any remaining chemicals.

A neutralizing solution, such as sodium metabisulfite, is used to neutralize any residual acid and stop the chemical reaction.

• Washing and Rinsing:

1. Drying: The denim garments are then dried, either in industrial dryers or air-dried, depending on the desired finish.

• Finishing:

Softening: Softening agents may be applied to enhance the comfort and feel of the fabric.

Final Inspection: The garments undergo a final quality inspection to ensure the acid wash effect is consistent and meets the desired standards.

The result of the indigo acid wash process is a unique, vintage look with high contrast and irregular patterns, giving each garment a distinctive appearance. The process can be adjusted to achieve varying levels of distress and pattern intensity, depending on the desired style.

ALL THE ABOVE ARE COMMON BREIFING IN BD MARKET. WHAT WE ARE DOING IS COLLECTING INDIGO YARN FROM DENIM PROJECT, TRYING TO MAKE FABRIC WITH THE YARN AND FACING BELOW PROBLEMS:

• Head and tail of the yarn aren't same as its a rope dyeing.
• 399 cones are used to dye all together, not less or more.
• Yarn coning isn't possible as regular format i.o as baby cone as below:
• As the yarn has length wise shade variation for beam dyeing

• Beam to beam denim fabric doesn't required yarn coning, its a direct process of weaving from beam to beam. So no needed of yarn conning.

• When we used to re-cone the yarn and due to the shade difference of head and tail yarn cone got discontinuous shade variation to every cone which makes fabric barre.
• Think we have managed length wise yarn cone from denim and put all cones (1 set) to knitting machine and started knitting and after few hours one cone is finished and we are trying to put one new cone or another baby cone to the knitting machine. And this will again start barre.
• In these regards, wee need to put 1 set yarn to machine and if one cone finished, total set became wastage. And in total the wastage percentage will be huge.

Three innovative minds have collaborated to revolutionize the yarn dyeing process for indigo, moving away from the traditional denim factory constraints and addressing the problems faced. This breakthrough in textile research and development aims to enhance fabric quality and introduce new innovations in the BD market. The team members are:

• Syed Mehedi Hasan (+8801713215580): Textile Research and Development, Primeasia University
• Md Shelim Sharder (+8801711596439): Yarn Dyeing Researcher and Developer for both woven and knit, Bangladesh University of Textile
• R.U.M Shaikat (+8801713047982): Washing Researcher and Operational Head, University of Dhaka

Additionally, several colleagues contributed to this R&D effort.

Future Prospects

• Fiber Dyeing: This process can be further optimized for different fiber types, improving the evenness and quality of the fabric.
• Spinning Techniques: Advanced spinning techniques can be explored to enhance yarn strength and uniformity.
• Innovation: Continuous research and development will focus on new dyeing methods, sustainable practices, and innovative fabric treatments.

This new approach to indigo yarn dyeing, developed by Syed Mehedi Hasan, Md Shelim Sharder, and R.U.M Shaikat, along with their colleagues, aims to improve fabric quality and introduce innovative practices in the BD market. By focusing on fiber dyeing and advanced spinning techniques, this process promises more even and high-quality fabrics, setting a new standard in the textile industry.