Indigofera Tinctoria

The indigo plant, a native of Asia, but

cultivated and naturalized in many countries. The use of indigo as

a dye is of great antiquity. Both Dioscorides and Pliny mention

it, and it is supposed to have been employed by the ancient

Egyptians. The indigo of commerce is prepared by throwing the

fresh cut plants into water, where they are steeped for twelve

hours, when the water is run off into a vessel and agitated in

order to promote the formation of the blue coloring matter, which

does not exist ready formed in the tissues of the plant, but is

the result of the oxidation of other substances contained in them.

The coloring matter then settles at the bottom; it is then boiled

to a certain consistency and afterwards spread out on cloth

frames, where it is further drained of water and pressed into

cubes or cakes for market.