The popular method employed in all the indigo tracts appears to be the ‘wet-leaf’ method in which the stalks and leaves of the indigo plant were soaked to extract the dye. However this method had two variants: the single vat system and the two-vat technique. We have the testimony of Pelsaert that the first technique was prevalent in the regions of Mewat and Sarkhej, while the second prevailed in the Bayana and the Kol-Khurja tracts:
The method of manufacture [in Mewat] is that of Sarkhej rather than Bayana; the steeping of the plant, and the working back and forward to extract the dye from the leaves are done in a single put, whereas in Bayana or Gorsa [Khurja] two are used…
Tavernier is much more detailed when he explains this single-vat system in Gujarat. According to him:
The tanks are generally from 80 to 100 paces in circuit, and when half-full of water, or a little more, they are filled up with the cut plant. The Indians mix it and stir it up with the water every day until the leaf – for the stem is of no account – becomes reduced into slime or greasy earth. This done, they allow it to rest for some days, and when they see that all has sunk to the bottom and that the water is clear above, they open the holes made round the tank to allow the water to escape. The water having been drawn off, they then fill baskets with the slime, after which, in a level field, each man sits near his basket, takes this paste in his fingers, and moulds it into pieces of the shape and size of a hen’s egg cut in two – that is to say, flat below and pointed above. But the indigo of Ahmadabad is flattened and made into the shape of a small cake…
From the account of Peter Mundy it appears that the steeping and stirring of the stalks and leaves to extract indigo pigment took around 48 hours before the ‘water receaves the Coulour’.
This single-vat technique of manufacturing indigo was ‘inferior’ and resulted in a low quality of dye. This is specifically mentioned by a factor at Surat, who in
1648 wrote to Bayana:
…this sort will not come up to expectations as regards goodness; for it, being to my knowledge, made in one chebecha [chāhbacha] can not compare with what is made in Coriah [Khurja] itself.
Thus from these descriptions to appears that in this system there were single circular vats called chāhbachas (artificial wells; lit. sons of wells) which were used both for steeping and beating purposes to extract the indigo dye from the plant.
ASHA: Blast From The Past 