The practice of dying with indigo is an incredibly rich cultural tradition, with each region of the world having its own unique methods, beliefs and rituals as part of the process.
Woven linen fabric with indigo dyed borders survives from the Egyptian tombs dating from around 2400 BC . Reference to blue cloth being traded by the merchants of Sheba (now Yemen) can be found in the Old Testament. Wool and cotton tie dyed and resist dyed fabrics found in Mali date back to the 11th century. And these are but a few examples.
Fermented or bacterial indigo has been used as a dye since antiquity, after it was discovered that indigo leaves left to rot in urine would release colour and create a green solution. When soaked in this solution, natural fibres will then turn from green to blue when exposed to air.
The main plant genus that have been traditionally used for indigo dying are Indigofera, Polygonum, Lochocarpus and Isatis. These plants contain the chemical compound indican in their leaves.
Indigofera tinctoria belongs to the Leguminosae family, has light green foliage and pea like flowers and is native to India, China and parts of South America. The process of fermenting releases the dye.
Isatis tinctoria or Woad is a cool climate plant that has been grown commercially in Europe since medieval times. During the Middle Ages, woad was grown in abundance to supply the local weaving industry in Europe
Polygonum tinctorium also known as Japanese indigo, Chinese indigo or dyers’ knotweed, is often cultivated concurrently with Indigofera in China and Japan.
In Western Africa the Yoruba people use Lonchocarpus cyanescens to dye their intricate paste resist clothing, in shades of dark and light blue
Information from Prideaux, Vivien 2003, “A Handbook of Indigo Dying” Search Press Limited, Kent , UK
