Ink
a liquid or pigment used for writing or printing. Inks may be classed under four heads:
Writing inks consist either of colored liquids, or of finely divided colored precipitates suspended in a liquid. Red ink is a solution of cochineal or pure carmine in ammonia, or of brazil wood in water. Blue ink is a solution of Prussian blue and oxalic acid in water. Chrome ink is a preparation of logwood and potassium bichromate.
Marking ink must be able to withstand the action of soap, alkaline, and acid liquids. It usually consists of a solution of silver nitrate, colored with lampblack and thickened with gum.
Copying ink must be thicker than ordinary ink, and must not dry too quickly. It is usually prepared by adding a little sugar or glycerine to ordinary black ink. Its sp. gr. should not exceed 1.071.
Printing ink. All inks used for printing consist essentially of well boiled drying oils, mixed with lampblack or other pigments. Soaps and resinous matters are frequently added to give the oils the required consistency.