The Economic Aspects of Historic Indigo

Indigotin, the main constituent of indigo, is prepared from the leaves of various species of Indigofera. Only about four ounces of indigotin are extracted from 100 pounds of plant material, according to a 20th century source. Preparation for market requires many steps: First the plants are cut just as the mature, then steeped and allowed to ferment; next the solution containing indigotin is drawn off and the plants are disposed of; the indigotin solution is then subjected to another series of steps. The solution is beaten with paddles to incorporate air into it and to promote oxidation. When oxidation is complete, the indigo material is allowed to settle, the liquid is drawn off, and the mass of indigo , pressed, cut, and dried, is ready for market.

Early in the 19th century, indigo was often sold in the forms of dark blue cubes or cakes called "junks". The quality of these "junks" was a matter of great concern to the professional dyer, for indigo was an expensive dye. If, as one dyer stated, 6 ½ pounds of indigo would dye 100 pounds of cloth a full deep blue, the cost of indigo alone per pound of cloth dyed would be more than .$.14, based on the 1831 price of $2.25 per pound (Lynde, p.8). The cost of indigo and other indigo dye ingredients such as potash, bran, and madder, plus labor costs, added up to a very costly dye operation.

Opinions differed greatly on which country exported the best grade of indigo. Some dyers considered Bengal indigo the best, claiming that it would color at least 10 % more cloth than the best Spanish Flote indigo, imported from the Spanish dominions in central America. The criteria by which the 19th century dyer judged the quality of indigo included: light weight in relation to bulk, smoothness in fracture, and a bright violet, purple, or bronze hue.

There was a general agreement that the price paid for the indigo should be in proportion to its yield. Thus sometimes buying low-priced indigo with moderate yield could be more profitable than purchasing the highest priced article with proportionateley lower yield.