What Is the Soda Ash for in Tye Dye?

Soda ash is a necessary ingredient when using fiber reactive dyes to tie dye.

Soda ash, whose chemical name is sodium bicarbonate, is the active ingredient in washing soda and is also used as a water softener. It can be extracted from the ashes of plants or made synthetically out of ordinary table salt. In tie dying and other types of dying, soda ash is used to fix the dye to cotton fibers in cloth.

Purpose

Soda ash is an alkaline and is used when dying with fiber-reactive dyes to increase the pH of the dye. This helps the dye to attach to the fabric. For most fiber reactive dyes, a high pH is needed to activate the cellulose in the cotton fiber. The soda ash and cellulose combine to form an anion, which attracts the dye molecules so that a very strong, permanent bond is formed between the fiber and the dye molecule. This bond causes the dye to be fixed to the cloth so that it does not wash out. Soda ash can be used with cotton and silk, but not other protein fibers such as wool. Soda ash is used to increase the pH, rather than other chemicals, because it is relatively safe and cheap to use, compared with other strong alkaline substances.

Sources

Although soda ash is a common ingredient in washing soda, it is usually mixed with brighteners or fragrances. A better source of cheap soda ash is found in swimming pool supply stores, which usually carry pure soda ash, used to increase the pH of pool water and making it hard for bacteria to grow.

Use With Dyes

Soda ash does not fix all types of dye to fabric. For example, it will not fix all purpose dyes, such as Rit. These types of dye require chemicals called cationic fixatives to be made wash-fast, so the colors do not run when washed. Soda ash only works as a fixative when used with fiber reactive dyes, such as Procion MX.

Method For Tie Dye

In tie dye, the usual method is to add the soda ash before adding the dye. The cloth is first tied as desired. Then it is soaked in a solution made of 1/2 or 1 cup of soda ash per gallon of warm water. Soda ash dissolves best at around 96°F. After soaking, the fabric is wrung out or dried and then placed in the prepared dye. The soda ash is not washed out of the cloth before dying.

Warning

Soda ash is very alkaline and can burn or damage skin or cause a rash, so you should wear gloves when handling it or when handling fabric that has been soaked in a soda ash solution. Soda ash dust can also irritate the skin and lungs, so be careful not to breath in large amounts.

References

• Paula Burch: All About Hand Dyeing
• True Tie Dye: How to tie dye