Indigo Dye Vat using Yeast and Sugar
Although indigo powder is blue, the indigo molecule does not produce its blue colour until it is oxidised. The indigo blue powder must be dissolved in an alkali bath with the combined oxygen removed. This method uses a combination of yeast and sugar:
- Fill the dye pot with water at 40°C and add 3 tablespoons of sugar and 2 tablespoons of dried yeast. Stir well.
- Leave until the yeast starts to froth.
- Dissolve 2 tablespoons of washing soda (soda ash) in hot water and stir in 2 or 3 teaspoons of indigo powder. Mix well to ensure all the indigo particles are incorporated.
- Stir this paste into the yeast mixture in the dye pot, cover with an airtight lid and put in a warm place. Keep the temperature constant and do not allow it to get above 50°C.
- Allow to stand (about 48 hours) until the liquor turns a greenish, yellow colour.
- Carefully immerse the yarn, fibres or fabric into the vat (you don’t want to add any oxygen). Leave for 25 minutes.
- Have a bowl of clean water ready, and equally carefully remove the yarn, fibres or fabric so that there are not drips back into the vat to create air bubbles. The yarn, etc. will start to turn blue, quickly plunge them into the clean water to remove any undissolved spots of indigo.
- Remove from the water and allow the colour to develop in the air.
- If you need a deeper colour, carefully re-dip the yarn, etc. Repeat as many times as you want to get the colour depth required. Once colour is reached, rinse thoroughly, then wash and rinse again.
Indigo Dye Vat using Yeast, Sugar and Ammonia
- Combine 1 tablespoon powdered yeast (bread yeast), 1 cup warm water and 1 rounded tablespoon sugar and let stand in a warm place for about 2 hours.
- Dissolve 2 level teaspoons natural indigo in ½ cup non-sudsing Ammonia and leave to sit for about 2 hours.
- After 2 hours, combine the indigo and ammonia to the yeast/sugar solution in a half-gallon jar. Fill to the top with warm water, stir once, cover with plastic wrap, using a rubber-band to seal. Don't use a rigid seal, the fermentation can burst it. Let this jar sit for several days in a warm place. The liquid will clarify to an even yellow which means that the yeast has removed all the oxygen, enabling the indigo to dissolve. If your jar stays blue, add more yeast (if this doesn't do it, add more sugar also).
- When the mixture has reached the yellow stage, immerse some pre-wetted fiber, and leave in over-night. Remove carefully (not dripping into the jar, which will add oxygen) and hang in the air for 20-30 minutes. Repeated dips will deepen the color.
- Once the desired shade has been achieved, rinse well. The not-very-pleasant smell will disappear from your dyed goods with the final rinse.
Jam Jar Method
This method is very useful for experimenting with small amounts of different fibres:
- Fill the jam jar with water at 40°C and add 3 teaspoons of sugar and 2 teaspoons of dried yeast. Stir well.
- Leave until the yeast starts to froth.
- Dissolve 2 teaspoons of washing soda (soda ash) in hot water and stir in ½ teaspoons of indigo powder. Mix well to ensure all the indigo particles are incorporated.
- Stir this paste into the yeast mixture in the jam jar, cover with an airtight lid and put in a warm place. Keep the temperature constant and do not allow it to get above 50°C.
- Leave to stand for about 48 hours until the liquor turns a greenish, yellow colour and immerse fibres etc as above.
Before dyeing, it is important to check whether the item is 'Prepared for Dyeing' (PFD) or requires scouring to remove any grease, oil or starch. Run a few droplets of cold water onto the fabric. If they soak in quickly, no scour is necessary. To remove starches, size and oils, add 5mls of Synthrapol (a non-ionic detergent) along with 2-3 litres of water for each 100gms of material. Stir gently over a 15 min period, and then rinse thoroughly in warm water. It is possible to use household detergent, but the alkaline residue may affect the final colour or wash fastness.