THE INDIGO PLANT 



Plants to the 

 Acre. 



INDIGOFERA 



Manufacture : 

 "Wet Process 



serious in those lands which have been sown in indigo for several years in 

 succession, and that a reasonable system of rotation would reduce the 

 injury to a negligible quantity." 



" Of other insect pests which assume dangerous proportions, there is 

 Aphides. an Aphis and a Thi-ips, but little or nothing is known of the life histories 



of either. They both attack the young plant, rendering it stunted, and 

 the latter, by destroying the mesophyll of the cotyledons and first foliage 

 leaves, may kill the entire plant " (Leake). [Cf. Lefroy, Caterpillar 

 Pests of Indigo in Bihar, in Agri. Journ. Ind., 1906, i., pj;. iv., 

 338-50.] 



Yield. Outturn and Yield. " Owing to the numerous variations in the exact 



area denoted by the term bigha, and to the confusion consequent thereon, 

 it is almost, if not quite, impossible to determine with any degree of cer : 

 tainty from the published returns what is a normal yield of plant and dye. 

 Under these circumstances it seems best to give the returns for a particular 

 concern for which the figures are available and which, being situated in 

 the centre of the indigo districts of Bihar, may fairly be taken as normal. 

 The period from which the averages are derived covers a term of eleven years, 

 viz. from 1892-1903. This shows an average of 80 maunds of plants per 

 acre for the morhun cutting, and 35 maunds of plants per acre for the khunti 

 Dye to the Acre, cutting, while the dye manifests an average of 16 Ib. per acre for the year, 

 in the proportion of 11 Ib. for the morhun and 5 Ib. for the khunti cutting. 

 The fluctuations are, however, very wide, e.g. for plant per acre 168 to 

 48 maunds, and for dye, 25 Ib. to 7| Ib " (Leake). 



MANUFACTURE. 



WET PROCESS. " For the manufacture of dye from the plant, the 

 wet process is now almost invariably adopted. Briefly this consists in the 

 extraction from the plant of the dye-yielding principle by steeping in 

 water, and the precipitation, from the extract so obtained, of indigo by 

 exposure to air oxidation. As the amount of plant which must be daily 

 steeped comes to some hundreds of cartloads, there are certain essentials 

 which must be considered in choosing a site for a factory. Chief among 

 these is an abundant supply of water ; and a factory will never, therefore, 

 be found at a distance from a stream or large lake, from which water can 

 be pumped into a large tank khazanah placed at the highest point of 

 the factory. From this tank channels conduct water to the steeping vats, 

 a row of brick and cement-lined basins, usually about 20 feet square and 

 4 to 5 feet deep, and about 15 in number. Below these, and corresponding 

 with them in number, are a second row of slightly shallower vats called the 

 beating vats. 



" The plant, on arrival at the factory, is loaded into the steeping vats 

 and, as soon as each vat is full, is battened down by means of beams at- 

 tached to pegs set in the sides of the vat. Water is now run in until the 

 plant is just submerged, and steeping is allowed to proceed for a period 

 varying from 12 to 14 hours. The liquor, which has by this time become 

 yellowish green and almost fluorescent, is now run off into the lower, or 

 beating vat. 



Beating Vats. " Beating is effected in various ways, the sole object being to obtain 



as thorough an oxidation as possible. In the more primitive method 10 

 to 12 coolies enter the vat and proceed to beat the liquor with short sticks 

 to one end of which flat discs of wood are attached. The process is com- 

 plete after about 1^ hours' continuous beating. With the introduction 



680 



Manufac- 

 ture: 

 "Wet 

 Process. 



Site of Factory. 

 Water Supply. 



Steeping Vats. 



