Carmine, the coloring matter of cochineal. To separate it, cochineal is exhausted with boiling water, and the clear decanted liquid is treated with cream of tartar, alum, or acid oxalate of potassium. The fatty and albuminous matters then coagulate, and carry down the coloring matter with them. By treating a solution of cochineal with an alkaline carbonate and alum, a compound of the coloring matter with alumina is obtained, known by the name of carmine-lake. The cheaper sorts of carmine are sometimes adulterated with extract of Brazil wood and cheaper vermilion. Cochineal colors are used for dyeing wool and silk crimson or scarlet; but the colors are not very durable, and are easily soiled by water or alkalies. Carmine is also used in the manufacture of red ink, as a cosmetic, as a pigment in water colors, and in the preparation of artificial flowers. It is said that the color was accidentally discovered by a Franciscan monk at Pisa, who was engaged in preparing a medicine of cochineal and salt of tartar. - Several processes are in use for the preparation of carmines, one of the best of which is thus given in the Annates de VIndustrie: Two pounds of the finest cochineal in powder are to be put into a vessel containing six pailfuls of boiling soft water; and the boiling is to be continued for two hours, when three ounces of pure saltpetre, and soon after four ounces of binoxalate of potash, are to be added.
After ten minutes the boiling is to be discontinued, and the liquor is allowed to stand for four hours. It is then to be drawn off with a siphon into flat glazed dishes, and left for three weeks. A coating of mould forms upon the surface, which is to be nicely removed in one piece; or if any fragments remain, they must be taken out with the greatest care. The liquor is again to be drawn off with a siphon, leaving the cake of carmine in the dish, when it is to be carefully dried in a clean shady place. As carmine is desired to be used principally as rouge, for imitating the soft blush upon the fairest cheeks, it is an especial object to obtain it of the highest degree of perfection; and so delicate are the processes of the French that the result is affected by the condition of the weather, and the best carmine is only made on bright sunny days. Sir Humphry Davy relates an incident of an English manufacturer agreeing to pay £1,000 to a Frenchman for the secret by which the latter made so superior an article; when it appeared that the only difference in the two modes of preparation was that the Frenchman always selected such fine bright weather as the Englishman could not hope to command in his own country. (See Cochineal).