Soda Ash (Sodium Carbonate)

Soda ash (sodium carbonate) is one of the most useful helpers in natural dyeing. It cleans (scours) cotton and linen before dyeing, it is used with alum when mordanting plant fibers, and it shifts madder toward redder tones. It is also used to raise the pH of indigo vats.

Sizes: 50 g (1.76 oz), 100 g (3.5 oz) and 400 g (14.1 oz).

How much soda ash to use

• Scouring cotton and linen: 2–5% WOF with a little pH-neutral soap. Simmer for about an hour, then rinse well.
• With alum on cotton and linen: 1.5–2% WOF together with 12–15% alum, after a tannin bath.
• Madder: a small pinch in the rinse or dye bath shifts color toward red and pink.

How to scour cotton and linen

1. Weigh the dry fabric and weigh 2–5% soda ash.
2. Dissolve the soda ash in hot water in a large pot, add a drop of pH-neutral soap and the wet fabric.
3. Simmer for about an hour, stirring now and then. You will see the water turn yellow or brown as oils and starch come out.
4. Rinse well. The fabric is now ready to mordant.

Important

• Do not use soda ash on wool or silk. It is too alkaline for protein fibers; wash them with a pH-neutral soap instead.
• When mordanting, dissolve soda ash and alum separately: they fizz when combined.
• Wear gloves; soda ash is mildly irritating to skin and eyes.

Related: How to prepare fabric for natural dyeing · Mordanting cotton and linen · Cellulose mordant kit

Frequently asked questions

What is soda ash used for in natural dyeing?

Scouring cotton and linen, helping alum bind to plant fibers, shifting madder toward red, and raising the pH of indigo vats.

Can I scour wool with soda ash?

No. It is too alkaline for wool and silk. Use a pH-neutral soap instead.

How much soda ash do I need to scour fabric?

2–5% of the dry fabric weight, so 2–5 g for 100 g of cotton or linen.

Read the guide: Soda ash, chalk and gum arabic guide

Work out exact grams for your fabric with our free natural dye calculator and WOF chart.