With pictures of Loren and her indigo pot at Faire
This dye has been used since Neolithic times in Europe. It was highly prized for its colour and light fastness. Until the end of the 19th century, the sole source was from plants, woad (Isatis tinctoria) and Dyer's Knotweed (Polygonum tinctorum) in temperate climates and Indigofera species in the tropics. Woad was widely grown in Europe, making some regions, especially Toulouse (France) and Erfurt (Germany), very wealthy until the end of the 16th century. After that time, it was used to make a woad vat for dyeing with indigo from India.
Indigo refers to several species of Indigofera, famous for the natural blue colors obtained from leaflets and branches of this herb. Of primary importance are French indigo, Indigofera tinctoria, and Guatemalan indigo, Indigofera suffruticosa , which was formerly classified as Indigofera anil . Prior to the development of synthetic indigo dyes, the indigo species were grown commercially in the East Indies, India, and parts of North, South, and Central America for export and domestic use. Popularity and economic value of the plant reached a peak during the Middle Ages, when indigo was the most important dye plant for blue color in the western portion of the world The dye is produced during fermentation of the leaves. A paste that exudes from fermenting plant material is processed into cakes and finely ground. The blue color develops as the material is exposed to air. Today almost all indigo for dyeing cotton and wool is synthesized commercially. This information courtesy of www.napagarden.com.
The cut plant is tied into bundles, which are then packed into the fermenting vats and covered with clear fresh water. The vats, which are usually made of brick lined with cement, have an area of about 400 square feet and are 3 feet deep, are arranged in two rows, the tops of the bottom or "beating vats" being generally on a level with the bottoms of the fermenting vats. The indigo plant is allowed to steep till the rapid fermentation, which quickly sets in, has almost ceased, the time required being from 10-15 hours. The liquor, which varies from a pale straw colour to a golden-yellow, is then run into the beaters, where it is agitated either by men entering the vats and beating with oars, or by machinery. The colour of the liquid becomes green, then blue, and, finally, the indigo separates out as flakes, and is precipitated to the bottom of the vats. The indigo is allowed to thoroughly settle, when the supernatant liquid is drawn off. The pulpy mass of indigo is then boiled with water for some hours to remove impurities, filtered through thick woollen or coarse canvas bags, then pressed to remove as much of the moisture as possible, after which it is cut into cubes and finally air-dried.
Nature 1 November 1900