Indigo

From Encyclopediak

Indigo, a blue dye obtained from a number of tropical plants of the Pulse Family. It was once widely used in the production of the color which has received its name. Since indigo has been produced artificially from coal-tar products, the importation of indigo is comparatively small. The indigo plants are perennial shrubs that grov to a height of about six feet and have compound leaves and pink or purple blossoms. In the preparation of dye the plants are cut just before they blossom and are steeped in water for from 12 to 15 hours. The steeping vats are practically without air, and the fermentation which the stalks undergo there produces a liquid known as indigo white. This liquid is drawn off and churned violently until the muddy indigo blue forms, because of contact with the air, and sinks to the bottom of the vat. When this has fully settled, the liquid is allowed to run off and the indigo blue is collected, squeezed as dry as possible and further dried in air. It is sold in lumps or as powder. Indigo plantations were common in India, and the dye was brought in large quantities to the Mediterranean countries by traders from the East.