CRAFTS OF INDIA / TIE & DYE / TYPES

CRAFTS OF INDIA / TIE & DYE / TYPES

The above outlines the simple method of tie & dye. More sophisticated tie-dyes involve additional steps, including an initial application of dye prior to the resist, multiple sequential dye and resist steps, and the use of other types of resists (stitching, stencils) and discharge.

A variety of dyes can be used in tie-dyeing, including household, fiber reactive, acid, and vat dyes. Most early (1960s) tie-dyes were made with retail household dyes. In order to be effective on different fibers, these dyes are composed of several different dyes, and thus are less effective, and more likely to bleed and fade, than pure dyes designed for specific fibers.

Protein-based fibers such as silk, wool, and feathers, as well as the synthetic polyamide fiber, nylon, can be dyed with acid dyes. As may be expected from the name, acid dyes are effective at acidic (low) pH, where they form ionic bonds with the fiber. Acid dyes are also relatively safe (some are used as food dyes) and simple to use.

Most tie-dyes are now dyed with reactive dyes, a class of dyes effective on cellulose fibers such as cotton, hemp, rayon, and linen. This class of dyes reacts with fibers at basic (high) pH, forming a wash-fast, permanent bond. Soda ash (sodium carbonate) is the most common agent used to raise the pH and initiate the reaction, and is either added directly to the dye, or in a solution of water in which garments are soaked before dyeing. Procion dyes are relatively safe and simple to use, and are the same dyes used commercially to color cellulosic fabrics.

Vat dyes including indigo, are a class of dyes that are effective on cellulosic fibers like cotton and silk. Vat dyes are insoluble in water in their unreduced form, and the vat dye must be chemically reduced before they can be used to color fabric. This is accomplished by heating the dye in a strongly basic solution of sodium hydroxide (lye) or sodium carbonate (caustic potash) containing a reducing agent such as sodium hydrosulfite or thiourea dioxide. The fabric is immersed in the dye bath, and after removal the vat dye oxidizes to its insoluble form, binding with high wash-fastness to the fiber.

However, vat dyes, especially indigo, must be treated after dyeing by 'soaping' to prevent the dye from rubbing off. Vat dyes can be used to simultaneously dye the fabric and to remove underlying fiber-reactive dye (i.e., can dye a black cotton fabric yellow) because of the bleaching action of the reducing bath. The extra complexity and safety issues (particularly when using strong bases) restrict the use of vat dyes in tie-dye to experts.

Also known as hot water dyes, direct dyes can be used with hot water and require no binding or exhausting agents. They are convenient but lack in color fastness and wash fastness. They are used on cotton, wool, silk and nylon. The colors of direct dyes are duller than those provided by reactive dyes. They can be found in powder form as well as in the form of a liquid concentrate. They do not require any form of ‘fixing’.

These are two sets of chemicals which, upon reaction, produce a third chemical, essentially colorful in nature. The fabric is dyed with one and later printed with the other. The chemical reaction produces a third color. However, the biggest drawback of this process is that there are just a few chemicals available which produce colors upon reaction.

Procion fiber reactive dyes are specially formulated for cellulose fibers like cotton, linen and rayon. They also work well on silk. They are considered 'cold water'” dyes. These dyes make fabrics great for solar dyeing, tie and dye and batik. As for the auxiliary chemicals, all you need is salt and soda ash. Synthrapol is optional but very helpful for rinsing out excess dye. Procion fiber reactive dyes can also be used on protein fibers but different auxiliaries are needed and the dye bath must be simmered.

Discharge agents are used to bleach color from previously-dyed fabrics, and can be used in a sort of reverse tie-dye. Household bleach (sodium hypochlorite) can be used to discharge fiber reactive dyes on bleach-resistant fibers such as cotton or hemp (but not on wool or silk), though the results are variable, as some fiber reactive dyes are more resistant to bleach than others. It is important to bleach only as long as required to obtain the desired shade, and to neutralize the bleach with agents such as sodium bisulfite, to prevent damage to the fibers.

Thiourea dioxide is another commonly used discharge agent that can be used on cotton, wool, or silk. A thiourea dioxide discharge bath made with hot water is made mildly basic with sodium carbonate. The results of thiourea dioxide discharge differ significantly from bleach discharge. Discharge techniques, particularly using household bleach, are a readily accessible way to tie-dye without use of often messy and relatively expensive dyes.