Skein (Hank), Package, Warp-Beam and Piece Dyeing Techniques

Last updated on July 14th, 2023 at 12:49 am

Textiles are dyed at different stages like fibre, yarn, fabric, or garment form. In this article, we will discuss the following four dyeing techniques.

Skein (Hank) Dyeing

Yarn may be prepared in a skein or hank form and then dyed. It is used to dye yarn in large quantities. The loose arrangement of the yarn allows for excellent dye penetration. The skeins are hung over a rung and immersed in a dye bath in a large container. Skein dyeing is the most costly method, but the color penetration is best, and the yarns retain a softer, loftier hand. Skein-dyed yarn is used to a considerable extent for suiting and dressing goods.

It allows for efficient and consistent color application and is particularly suitable for natural fibers like cotton, wool, silk, and linen. Manufacturers can use this technique to achieve various vibrant and uniform colors in their textile products.

The general flowchart of the skein dyeing process

Preparation of Hank

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Pre-Treatment

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Dyes Preparation

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Dyeing

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Post-Treatment

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Drying and Finishing

Preparation of Hank

At first, the yarns are prepared by winding them into a skein or hank shape. A skein or hank is a long, continuous loop of yarns that can easily absorb dyes.

Pre-Treatment

Before dyeing, the yarns may undergo pre-treatment processes such as de-sizing, scouring, bleaching, or washing to remove any impurities, oils, or finishes that may hinder dye absorption.

Dyes Preparation

Dyes are prepared separately in a dye bath according to the recipe. The type of dye used depends on the desired shade and the type of fibre being dyed. The dyes can be synthetic or natural and come in various forms, such as powder, liquid, or concentrated solution.

Dyeing

According to the recipe, the prepared dye solution is heated and maintained at a specific temperature suitable for skein dyeing. The skeins are then carefully immersed in the dye bath, ensuring that they are fully submerged and allowing the dye solution to penetrate evenly. During this time, the dye molecules bind to the fibers of the yarn, resulting in coloration.

Post-Treatment

The skeins are rinsed once the desired shade matches to remove excess dye. This is typically followed by a washing process to remove any residual dye and improve color fastness. Here are some additional chemicals like fixing agents and pH adjustments needed.

Drying and Finishing

After post-treatment, the skeins are usually dried using specialized drying equipment. Once dry, the yarn is wound into cones in the winding machine for further processing.

Package Dyeing

Yarn wound on spools, cones, or similar units and then dyed is referred to as package-dyed yarn. The packages of yarn are stacked on perforated rods in a rack and then immersed in a tank wherein the dye is forced outward from the rods under pressure through the spools and then back through the packages toward the center to penetrate the entire yarn as thoroughly as possible. Most carded and combed cotton that is used for knitted outerwear is package-dyed.

The general flowchart of the package dyeing

Yarn Package Preparation

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Dye Bath Preparation

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Loading the Packages

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Dyeing

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Reductive Rinsing

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Oxidation and Soaping

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Unloading

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Hydro Extraction

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Drying

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Quality Control

Yarn Package Preparation

The grey yarns are wound onto a dye tube using a winding mechanism such as a precision or drum winder to make a cheese package. The dye tubes can be made of various materials, such as plastic, metal, or cardboard, but plastic dye tubes are used for dyeing.

Dye Bath Preparation

According to the recipe, the required dyes, along with necessary chemicals and auxiliaries such as hydrose, caustic soda etc., are added to the reserve tank of the dyeing machine. The reserve tank is usually heated up to 650 C and stirred to ensure proper mixing of the dyes and other chemicals.

Loading the Packages

The prepared packages are loaded onto rods or carriers and placed into the dyeing tank of the dyeing machine.

Dyeing

The loaded carriers with packages are immersed in the dyeing tank. Then the mixed liquor is pumped over the dyeing tank. The dyeing tank temperature and duration vary depending on the type of yarn being dyed and the specific dye used. The dyeing tank is often agitated or circulated to ensure even dye penetration.

Reductive Rinsing

After the desired dyeing time has elapsed, the carriers with packages are kept or removed from the dye bath and reductive rinsed to remove excess dyes and chemicals. Here are some substances such as caustic soda, hydrose and washing chemicals are used.

Oxidation and Soaping

Oxidation and soaping are two essential steps in the yarn dyeing process, particularly for dyes that require oxidative fixation. In different dyes, such as reactive, vat or direct dyes, the dye molecules undergo a chemical reaction called oxidation to fix them onto the yarn fibers. After the oxidation step, the yarn undergoes a thorough rinsing and washing process known as soaping. Soaping helps to remove any unfixed dye molecules, impurities, or residues that may remain on the yarn after the dyeing and oxidation stages. Chemicals like hydrogen peroxide, caustic soda, stabilizers and washing chemicals are used.

Unloading

After oxidation and soaping, the package carrier is unloaded from the dyeing machine for hydro-extraction.

Hydro Extraction

Then hydro-extraction of yarn packages are done to remove excess water for proper drying. The process involves using high-speed centrifugal force to extract water, reducing drying time and energy.

Drying

After hydro-extraction, packages are typically dried by air-drying or specialized drying equipment. The drying process removes any remaining moisture and ensures proper finishing.

Quality Control

Finally, the dyed packages are inspected for color matching and other defects. Samples may be taken for colorfastness testing, physical testing and other quality checks before the dyed yarn is ready for further processing.

Warp-Beam Dyeing

This method is similar to package dyeing but is more economical. Yarn is wound onto a perforated warp beam, immersed in a tank, and dyed under pressure. It is used when fabrics are to be woven with a dyed warp yarns.

The general flowchart of the warp-beam dyeing

Warp-Beam Preparation

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Pre-Treatment

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Dye Solution/Bath preparation

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Loading the Warp-Beam

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Dyeing

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Rinsing

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Finishing

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Drying

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Packaging

Warp-Beam Preparation

Warp-beam preparation is the first step of warp-beam dyeing. The yarns of a specific count to be dyed are determined based on the desired end product. The yarn is wound onto a warp beam, a cylindrical device used in weaving.

Pre-Treatment

In this step, de-sizing, scouring and bleaching are done to remove any impurities, oils, dirt, or finishes that might affect the dyeing process or final color. These processes typically involve washing the yarn with detergents, soaps or other cleaning agents.

Dye Solution/Bath preparation

According to the recipe, appropriate dyes, auxiliary chemicals, etc., are selected. Then the dyes and chemicals are mixed with water in the reserve tank to make the dye solution. Here, specific time, temperature and liquor ratio are adequately maintained.

Loading the Warp-Beam

The warp beam is now placed onto the dyeing machine. The yarns are threaded through the dyeing machine, ensuring that these pass through the necessary guides, tensioning devices, and other components.

Dyeing

After placing the warp beam onto the dyeing machine, the dye solution is pumped over the main dyeing tank. Specific time and temperature are maintained according to the dyeing recipe. The dye bath is circulated within the machine to ensure the even distribution of the dye solution. In the case of disperse dye, high temperature and pressure are applied for proper dyeing.

Rinsing

After dyeing, the dye solution is drained from the dyeing machine. The dyed yarn is rinsed thoroughly to remove any excess dye, residual chemicals, or impurities. Multiple rinsing cycles may be performed to ensure proper removal.

Finishing

For finishing, softening agents, fixing agents, or other chemicals improve the yarn’s feel, appearance, and colorfastness. The finishing chemicals are applied after rinsing or in a separate treatment step.

Drying

To remove the excess water from the warp beam, hydro-extraction is done. Then the warp beam is transferred to a designated drying area or specialized drying equipment, such as a drying cabinet or dryer. Proper drying ensures complete evaporation of moisture from the yarn.

Packaging

The dried yarns are then rewound onto a weaver beam or wound onto other packages, such as cones or hanks, for storage or further processing.

Piece Dyeing

The great bulk of dyed fabric on the market is dyed in the piece form. This method gives manufacturers maximum flexibility for their inventories to meet large or small demands for a given color as fashion requires. Where yardage warrants it, fabrics are dyed in continuous range machines. Small lots of fabrics of all fibres are dyed in batches. Piece dyeing is thoroughly satisfactory regarding levelness, penetration, and overall fastness, summing that the proper dyes have been used.

Fabric may be piece-dyed, whether it is composed of only one kind of fibre or yarn or blends of different fibres or combinations of different yarns. When the fabric is made of fibre or yarn, dyeing is relatively uncomplicated because the one appropriate dye is used. However, when the fabric contains a blend of fibres or a combination of different yarns, special procedures are required to employ other dyes that are each specific for the particular fibres used. These procedures are called union dyeing and cross-dyeing.

The general flowchart of the Knit dyeing

Loading

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Pre-Treatment

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Dye Solution Preparation

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Dyeing

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Rinsing

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Finishing

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Drying

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Packaging

Loading

The fabric roll is loaded into the dyeing machine by nozzle through the guide. After the whole fabric roll is loaded into the machine, both ends of the fabric are knotted together.

Pre-Treatment

Pre-treatment of the grey fabric is mandatory for proper dye absorption, shade matching and finishing. It also removes the grey fabric’s impurities, finishes, or sizing agents. Pre-treatment can involve processes like de-sizing, scouring, bleaching or washing.

Dye Solution Preparation

Now, according to the dyeing recipe and fabric type, appropriate dyes and auxiliary chemicals are selected. Then, dyes and auxiliary chemicals are mixed with water to prepare the dye solution. Here specific time, temperature and liquor ratio are maintained.

Dyeing

Now the fabric is immersed in the dye bath, and the bath is agitated or circulated to ensure even dye distribution and penetration. According to the recipe, fabric and dye type, specific heat, pressure and time are maintained.

Rinsing

After dyeing, the excess dye solution is drained from the dyeing machine. Then the dyed fabric is rinsed thoroughly to remove excess dye, residual chemicals, and impurities. Multiple rinsing cycles may be performed to ensure proper removal.

Finishing

Finishing is done in the stentering machine. Here the desired finishing treatments like width control, spirality control, GSM control etc. are done to the dyed fabric. This also includes the processes such as softening, anti-static treatment, or adding special effects like wrinkle resistance or water repellency. The finishing treatments enhance the fabric’s properties, appearance, or performance.

Drying

The stentering process also dries the finished fabric. During the drying process, adjustment and control of fabric width, heat setting, moisture control etc., are done.

Packaging

After finishing and drying processes, the dyed knit fabric rolls or panels are rolled, stacked, and packaged for storage, shipment, or further processing.