45 °

DYEING AND CALICO PRINTING.

on the colour of the liquor becomes gradually pale green, and the indigobecomes visible, being in a state of suspension as a flocculent matter. Assoon as this change is complete the workpeople leave the tanks, and, after theliquid has been left at rest for a time, the supernatant water is run off graduallyby the opening of plugs placed from the top to near the bottom of the tanksat convenient distances apart. The water flows again into the river, andthe precipitated indigo, in the form of a thickish semi-fluid mass, runs along aspout into a well-construdted tank. This mass is next drawn up by the aid ofa hand-pump, and conveyed to a large cauldron, where it is boiled with theview of preventing a further fermentation, which would spoil the produce byturning it black. After having been left at rest for twenty hours in thecauldron, of which, in a large fadtory, there are at least five often heated bymeans of steam, the pasty mass is boiled again for from three to four hours,and next, while yet hot, run on to a large filter, constructed in the followingmanner:—In a large tank of masonry of 6 by 2 metres and o'g metre deep,are placed pieces of bamboo cane, over which are spread lightly woven mats,and next over these a strong piece of sail-cloth. Upon this latter remains athick deep blue, nearly black, paste; the water collected in the tank stilldeposits some indigo, and is therefore boiled up again the next day, and after-wards filtered. The pasty and still very soft mass which remains upon thesail-cloth is removed to small wooden boxes, perforated with holes, andlined inside with a stout and strong cotton tissue. These boxes having beenfilled, and a lid having been put on the top, likewise perforated, and so con-strudted as to fit in, not on, the boxes, care being also taken to place a pieceof cotton on the top, the boxes are placed under a screw-press, and pressurehaving been gently and gradually applied, the water is squeezed out as muchas possible, that liquid being run again to the filter tank to colledt any indigoit may yet contain. The pressure having been withdrawn the boxes areopened, and the contents, shaped like blocks of soap, are placed in the dryingroom ; this is a large and high brick building, containing a series of window-like openings, closed by Venetian blinds, so as to prevent the access of diredtsunlight; while, moreover, there are planted outside and close to the buildinglarge trees for the same purpose. The process ought to proceed very slowly;and it takes from three to five days to dry the contents of each box. Artificialheat is not required, but in case of heavy rain shutters are put up outside theVenetian blinds. As soon as the cakes of indigo are thoroughly dry they arepacked in well-made wooden boxes, the seams of which are made water-tightwith pitch, and are often lined with sheet zinc or tinned sheet iron. Afterhaving been packed the drug is sent to Calcutta, the chief market. Eachfermenting tank produces from 18 to 25 kilos, of indigo if the plant begrown on alluvial soil, and from 16 to 32 kilos, if cultivated on older for-mations. The quality of the former produce is, however, preferable to thatof the latter. The spent plant (after fermentation) is only used as manure.The plants shoot out again if properly placed in the soil, but the indigothey would produce would be altogether of a low quality, and not pay theexpense and trouble of the manufadture.

The details above quoted refer to the manufadture of indigo as carried onby European planters, provided with a sufficiently large capital to defray theheavy expenses of establishing works and beginning cultivation. The natives