The process of extracting indigo dye is quite complicated and involves a lot of labour. The plants are soaked in a vat or a sloping tank. Two or three people actually get into the tank and paddle the water continuously for two to three days. The blue rises to the top. The water is drained out. The remaining blue substance is taken out and made into cakes. The blue that emerges cannot be matched. It is believed that the term "blue collar" worker is derived from the indigo workers, who used to wear the cheap blue cloth. The process of extraction of dye is also difficult because of the strong odour that the vat emanates. Also, the vat should not be exposed to sunlight. It is buried in the ground, with only the neck showing. There is also a belief in India that working on an indigo extraction unit makes a woman sterile. Hence, only men used to undertake this job.It is easy to dye cotton with indigo dye, but the process becomes difficult with silk or wool.
Experts say that Egyptian mummy clothes from the third millennium BC had borders of indigo dyed stripes. Blue was a predominant colour in the funeral wardrobe of Tutankhamen. Blue is the only colour found in the earliest dyed linen fragment of ancient Israel and Palestine . The linen wraps of urns containing the Dead Sea scrolls carried symbolic geometric patterns in blue. Babylonian texts talk of garments dyed in blue and there is even one which gives the method for dyeing in indigo. The Bible speaks of "blue clothes and embroidered work" traded by the merchants of Sheba . Blue silk fragments of the third millennium B C have been found in China .
Till the second half of the 18th century, Bengal did not play a major role in the indigo tale. It was only subsequently that the East India Company "promoted" the cultivation and processing of indigo in Bengal and Bihar . In the 19th century, Bengal was the world's biggest producer of indigo in the world! An Englishman in the Bengal Civil Service is said to have commented, "Not a chest of indigo reached England without being stained with human blood".
So, the next time you pick up a tie and dye dupatta, a kalamkari bedspread or just a pair of denims, think of the long history of indigo and the hard work that has gone into making the colour that you like so much.