Lac Extract – a red dye extract from the scale insect Laccifer lacca which is found throughout India, south east Asia, Nepal, Burma, Bhutan and south China. It is found both in the wild and cultivated. The female lac insects invade host trees (mainly fig and acacia) and the insect secretes a resin that contains the red dye. When harvested, the resin is taken off the branches and is known as stick lac. The resin is also used to make shellac. The dye must be extracted from the resin before it can be used to colour cloth.
Lac extract yields crimsons to burgundy reds to deep purples. The colourant is similar to cochineal but colours achieved are warmer, softer, and more muted. The lac dye has high light and washfastness on silk and wool. 5-8% dye to WOF is all that is needed for a medium depth of shade.
Mordanting: use alum mordant at 15% WOF for protein fibres. For cellulose mordant with tannin at 8% WOF and then alum at 15%, or alum acetate at 8% – but note that lac extract has reduced light and washfastness on cellulose fibres.
Dyeing: Use at 10-15% WOF. Dissolve extract in water and simmer with fibre for 45 minutes, leaving overnight for richest colours. This dye is very sensitive to change in pH and develops to its fullest colour potential with the addition of cream of tartar at 6% WOF. The addition of an alkali like soda ash will yield plum purples and the addition of iron will give blackened purples.
Thiourea dioxide is a reducing agent for indigo and other vat dyes and is an excellent substitution for sodium hydrosulfite in color stripping and discharge. It is safer to use, has a greater strength, and has a better shelf life. It can be used for stripping cellulose fiber or bleaching wool or silk. It must be used in a well ventilated area or outside.
Cutch Extract – This powder is an extract prepared from steeping the wood of the Acacia catechu tree in hot water until a syrupy liquid immerges. This is dried and then ground into powder. It is common to most parts of India, Burma, Indonesia and Peru. Indian cutch is by far the most beautiful. It is a good source of colourfast shades of brown - cinnamon, nutmeg, and clove. Cutch extract contains tannin as well as the dye compound catechu. It is easily soluble in water. Cutch has excellent light and washfast properties. It requires 20-50% WOF to dye a medium depth of shade.
Mordanting: use alum mordant at 15% WOF for both protein and cellulose fibres (there is enough tannin in cutch so mordanting with tannin is not required).
Dyeing: completely dissolve the powdered cutch (sometimes cutch will come a little chunky) in boiling water and add it to dyebath.
Deeper colours can be achieved by first soaking the cutch extract in a weak mixture of caustic soda. Add 1 tsp lye or sodium hydroxide to 4 litres (1 gallon) of water. Soak for 1 hour. Then add more water and neutralize with acetic acid or vinegar to pH7. Add this neutral solution to the dyebath.
Fibres are then added and the dyebath is kept at a low simmer for at least two hours. Cutch does not easily exhaust and dyebaths can be used multiple times for lighter shades.
The alum mordant yields toffee browns. The addition of iron at 2-4% WOF yields chocolate browns, while a soda ash rinse will redden the cutch colour. The addition of 2% WOF hydrogen peroxide during the final 15 minutes of dyeing will darken cutch considerably. Allowing the fibre to cool down and sit in the dyebath overnight will give the darkest shades.