Note {4} — Chapter XXII

Note 4.—In Bengal Indigo factories artificial heat is employed to promote the drying of the precipitated dye; but this is not essential to the manufacture. Marco’s account, though grotesque in its baldness, does describe the chief features of the manufacture of Indigo by fermentation. The branches are cut and placed stem upwards in the vat till it is three parts full; they are loaded, and then the vat is filled with water. Fermentation soon begins and goes on till in 24 hours the contents of the vat are so hot that the hand cannot be retained in it. This is what Marco ascribes to the sun’s heat. The liquor is then drawn off to another cistern and there agitated; the indigo separates in flakes. A quantity of lime-water then is added, and the blue is allowed to subside. The clear water is drawn off; the sediment is drained, pressed, and cut into small squares, etc. (See Madras Journal, vol. viii. 198.)