What Is Soda Ash? Learn How It Keeps Colors Bright in Dyeing

It's the secret to a more permanently set fabric in the wash.

dip dyeing cloth in tub
Photo: Raymond Hom

When you're learning how to dye anything, you'll quickly discover that soda ash ($6.92, amazon.com) is key to keeping your colors bright. "Soda ash, also known as sodium carbonate, washing soda, or salt soda, is used with fiber-reactive dyes to produce brighter and more colorfast results," explains Micheals Maker Sam Spendlove of The Pretty Life Girls. "Fiber-reactive dyes require soda ash to activate and fix, while one-step dyes often include soda ash in the dye powder."

While soda ash itself is not specifically a brightener, Paula E. Burch, Ph.D, of All About Hand Dyeing says its high pH level enables cellulose fibers in cotton to chemically react with a fiber-reactive dye, such as Procion dye ($7.50 per color, walmart.com), to form a permanent chemical bond. "Since the dye is permanently attached to the fiber, it does not wash out and the colors stay bright," she explains. "However, soda ash does nothing to keep colors bright in other types of dye, such as all-purpose dye."

Interested in learning more about soda ash and how to use it in order to maintain bright, rich hues when dyeing? From tips for using it as a presoak to how to use it in the washing machine, hand dye experts share their insight ahead.

Handle soda ash carefully.

Before you can use soda ash to brighten your dyes, Burch says it's smart to take certain safety measures. "As with other household chemicals, it's a good idea to wear gloves to avoid skin exposure and a mask while measuring out the powder (so you don't breathe in any dust)," she says. "If you happen to get soda ash on your skin, rinse it off immediately, because it can cause irritation."

It's also important to point out that soda ash can only activate and fix dyes on fabrics composed of plant-based cellulose fibers, such as cotton, linen, and hemp. "Synthetic fibers do not react to soda ash and fiber-reactive dyes," Spendlove explains.

Presoak fabrics in soda ash before dyeing them.

To use soda ash as a pre-soak treatment, Liz Welker of The Pretty Life Girls says to simply add one cup of soda ash to a gallon of warm water, and stir until dissolved. "Soak your material in the soda ash mixture for 20 minutes," she advises. "Wring out the material—but don't rinse—and continue with dyeing."

Use soda ash to dye fabrics in the washing machine.

Believe it or not, fiber-reactive dyes that require soda ash to activate can be dyed in the washing machine. "The steps vary by brand, but should be included in the package instructions," Spendlove explains. "This process generally involves pre-dissolving soda ash in hot water, and adding it to the dye bath during the washing cycle."

Use soda ash for better tie-dye results.

To use soda ash to brighten your next tie-dye project, Burch says to dissolve a cup of soda ash in a gallon of water, and soak your cotton items in it for 15 minutes to make sure the soda ash has penetrated the fiber. "Squeeze out the extra water, then apply the fiber-reactive dye to the damp fabric," she advises. "Do not use all-purpose dye for tie-dyeing, because it runs and fades, whether or not you use soda ash."

Reuse soda ash.

While the dye will likely go bad soon after mixing, Burch says soda ash solution will stay good forever. "You can keep your bucket of soda ash and reuse it the next time you dye," she explains. "Just be sure that children and animals cannot access the stored soda ash."

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