Indigo Dye
Indigo dye is derived from the small green leaves of the Indigofera plant. Harvested before the plant's flowers bloom, the leaves are soaked and churned to release a navy blue froth. After separating the liquid and sediment, a deep blue paste is filtered, pressed into cakes, and dried to become indigo dye. Lime and natural sugars can be added to enhance the extraction process.
Indigo powder is initially insoluble in water but becomes soluble through the addition of a reducing agent in a hot dye bath, creating "white indigo." The fabric is dipped in this bath, and upon exposure to air, the dye reverts to its deep blue shade. This technique was widely used in pre-colonial India, both for dyeing fabrics and sometimes for printing.
Evidence of indigo dye dates back to the late Bronze Age in Egyptian tombs. Mentions of indigo appear in ancient texts such as the Atharvaveda and the Periplus of the Erythraean Sea. The Roman writer Pliny the Elder described the dye-making process, highlighting its widespread trade across India, West Asia, and the Mediterranean.
Indigo trade thrived with the expansion of the Abbasid Caliphate and Indian Ocean commerce. Genizah documents show a flourishing trade in mediaeval times, even using the Sanskrit term "nili" to name Arab merchants. Gujarat, Kabul, Aleppo, and Jeddah emerged as major trading hubs.
European involvement intensified in the Levant, where indigo prices set the tone for global markets. Despite its high cost, indigo's potency and durability led to its prohibition in Europe at times. Gujarat, Rajasthan, coastal Pakistan, and later Bengal were primary production centres. British policies and exploitation of workers marked the Bengal indigo industry.
Synthetic indigo emerged in the late 19th century, reducing natural indigo's prominence. Today, most indigo is synthetic, used in denim production. Natural indigo remains in niche use, and recent innovations include freeze-dried indigo crystals for quicker dyeing and indigo's application as a colourant in food and pharmaceuticals.
