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Portrait of a Man in a Red Turban by Jan van Eyck, 1433
Carminic acid is extracted from the female cochineal insects and is treated to produce carmine, which can yield shades of red such as crimson and scarlet. The body of the insect is 19–22% carminic acid. The insects are processed by immersion in hot water or exposure to sunlight, steam, or the heat of an oven. Each method produces a different colour that results in the varied appearance of commercial cochineal. The insects must be dried to about 30% of their original body weight before they can be stored without decaying. It takes about 80,000 to 100,000 insects to make one kilogram of cochineal dye.
The two principal forms of cochineal dye are cochineal extract, a colouring made from the raw dried and pulverised bodies of insects, and carmine, a more purified colouring made from the cochineal. To prepare carmine, the powdered insect bodies are boiled in ammonia or a sodium carbonate solution, the insoluble matter is removed by filtering, and alum is added to the clear salt solution of carminic acid to precipitate the red aluminium salt. Purity of colour is ensured by the absence of iron. Stannous chloride, citric acid, borax, or gelatin may be added to regulate the formation of the precipitate. For shades of purple, lime is added to the alum.
Cochineal beetle red
Gold & Silver