This article is about the pigment. For information about the color see Carmine (color).

Carmine is a pigment of a bright red color obtained from the cochineal insect, and the general term for a particularly deep red color.

Usage

Carmine is used in the manufacture of artificial flowers , watercolors, rouge, cosmetics and crimson ink, and in the painting of miniatures. Carmine lake is a pigment obtained by adding freshly precipitated alumina to decoction of cochineal.

Preparation

It may be prepared by exhausting cochineal with boiling water and then treating the clear solution with alum, cream of tartar, stannous chloride , or acid oxalate of potassium ; the coloring and animal matters present in the liquid are thus precipitated. Other methods are in use; sometimes egg white, fish glue , or gelatine are added before the precipitation.

The quality of carmine is affected by the temperature and the degree of illumination during its preparation, sunlight being requisite for the production of a brilliant hue. It differs also according to the amount of alumina present in it. It is sometimes adulterated with cinnabar, starch and other materials; from these the carmine can be separated by dissolving it in ammonia. Good carmine should crumble readily between the fingers when dry.

Chemical composition

Chemically, carmine is a mixture of carminic acid with alumina, lime and some other organic acids. Carmine's vivid colour comes primarily from carminic acid, and this component is sometimes extracted for use as a pure dyestuff.