Cochineal – is the most important of the insect dyes. The females of Dactylopius coccus colonize the prickly pear (nopal) cactus native to Mexico, Central and South America and the Canary Islands. Peru is currently the primary export country, shipping out over 4000 metric tons annually. This dye is found mostly in food, drugs and cosmetics. Cochineal has excellent light and washfastness and produces a powerful range of fuchsias, reds and purples. The colour changes with the mordants used and pH of the dyebath.
Although expensive, it is very concentrated. The bugs have a high dye content (carminic acid) and go a long way. You will need only 3-8% WOF 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%. If cream of tartar at 6% WOF is added to the alum mordanting bath or the dyebath, the colour achieved will be more towards Christmas red. With the addition of iron at 2-4% WOF to either the mordanting bath or the dye bath the colour will shift towards purple.
Dyeing: The colourant is first extracted from the dried insects. Gently grind the insects in a blender or use a mortar and pestle to crush them to a fine powder. Put this powder into a saucepan and cover with three inches of water. Boil for 30 minutes. Strain the liquid and set aside. Place the cochineal pulp back in the saucepan and again cover with water and boil for 30 minutes. Add this decanting to the first decanting. Repeat 2 more times. Some dyers will then keep the remaining pulp in a jar of water for several weeks and use in subsequent dyebaths.
The combined decantings are used to make a dyebath.
Cochineal is sensitive to acids and bases. The cochineal rich red can be shifted to orange with the addition of an acid (vinegar) and to a deep fuschia with the addition of an alkaline (soda ash). This sensitivity means the soaps used to pre or post wash your fibres must have a neutral pH.