Indigo, or indigotin, is a dyestuff originally extracted from the varieties of the indigo and woad plants. Indigo was known throughout the ancient world for its ability to color fabrics a deep blue. Egyptian artifacts suggest that indigo was employed as early as 1600 B.C. and it has been found in Africa, India, Indonesia, and China.
The dye imparts a brilliant blue hue to fabric. In the dying process, cotton and linen threads are usually soaked and dried 15-20 times. By comparison, silk threads must be died over 40 times. After dying, the yarn may be sun dried to deepen the color. Indigo is unique in its ability to impart surface color while only partially penetrating fibers. When yarn died with indigo is untwisted, it can be seen that the inner layers remain uncolored. The dye also fades to give a characteristic wom look and for this reason it is commonly used to color denim. Originally extracted from plants, today indigo is synthetically produced on an industrial scale. It is most commonly sold as either a 100% powder or as a 20% solution. Through the early 1990s, indigo prices ranged near $44/lb ($20/kg).
A Brief History of Indigo in the United States
Indigo, the dyestuff most widely used in America during the 18th and 19th centuries, is not a native of this country. It is a blue dye derived from the leaves of a leguminous plant which grew in India and Egypt long before the Christian era and later was used by the Romans in making an ink they called indicum. In the 16th century Portuguese, Dutch, and English traders brought it to Europe from India. The earliest known attempt to grow indigo in America is revealed in a tract dated 1649. From it we learn that indigo was planted with the notion that it would eventually prove ten times more profitable than tobacco, and that the planters hoped to grow enough indigo to take over India's profitable indigo trade. Since no more is heard of indigo cultivation in the colonies until about ninety years later, one assumes that the project failed. This indigo may have been the plant sometimes called wild indigo or yellow wild indigo.
Dutch settlers also attempted to grow wild indigo in New York City and Albany as early as 1650. Other scattered references to wild indigo appeared throughout the colonial period and in the later19th century. One informs us that as late as 1873 some South Carolina planters still cultivated it, contending that in spite of indigo's low price - $.75 a pound- it was still more profitable than cotton.
Introduction of a species of Indigofera to South Carolina in 1739 and its subsequent commercial success must be credited mainly to the intelligent and persistent efforts of Eliza Lucas Pickney. Her father, Governor of Antigua at the time, sent her seeds of various plants that might be suited to growing conditions in Carolina. After many trials she managed to produce enough indigo in 1747 to make up a shipment for England. It met with approval in England and remained the staple crop of the colony from the late 1740s until the war, reaching its peak in 1773, when 1,107,660 pounds were exported to England (Sheffield, 1784).
During the war this crop was neglected in favor of rice; after the conflict it could no longer compete with the cheaper but better quality East Indian variety. Thus, toward the turn of the 18th century cotton took over from indigo as Carolina's important crop. Georgia and Louisiana cultivated some indigo but never succeeded in making a large-scale commercial success of it.
The French had introduced indigo to Louisiana in 1718, and 10 years later its export began. With the help of French bounties, indigo production and exportation continued until later in the century when it was learned that cotton could be produced more profitably (Bishop, 1866, vol.1, pg. 348)
Natural indigo was used throughout the 19th century, for it was not synthesized until the 1870s, and more than 20 years passed before methods were devised for producing it in quantities and at prices suitable for marketing. Synthetic indigo has replaced that of natural origin to such an extent that natural indigo is not practically impossible to obtain in this country.