On the Manufacturing of Indigo in this Country. 



239 



er is the most difficult point in the wliole process of making indigo ; 

 for should not the fermentation be carried far enough, a considerable 

 loss of coloring matter will be the result. It is necessary, therefore, 

 to carry it on to a certain point, and to draw it off die instant it ar- 

 rives at that point ; and this can he known only by a skilful observer 

 who has obtained his knowledge by practice- 

 There is no chemical operation so difficult to describe as tliat of 

 fermentation, and I "alniost despair of making myself clearly under- 

 stood by practical workmen in the following description of the steep- 

 ing process- 

 Fermentation has been divided by chemists into four kinds, the 

 panary, vinous, acetic and putrefactive. The kind of fermentation 

 given in the indigo steeper is evidently of tliat kind called panary, or 



It is known to be the panary by the 

 large quantity of carbonic gas given out, which rising to the surface, 



the first stage of fermentation. 



with 



The 



difficult point for the operator to distinguish is when it arrives at diat 

 degree of fermentation, and begins to assume the acetic. The 



same 



difficulty occurs with the woollen blue dyer, and the losses so fre- 

 quently complained of, by tlie vats being out of order, and often irre- 

 vocably lost, arise from the fermentation being permitted to proceed 



too 



The following directions are 



;iven as a guide for those who may 



be engaged in die making of indigo. Wh 



make 



strokes on white paper. The first will probably be high colored, 

 in which case die indigo is not sufficiently fermented. This opera- 

 tion is to be repeated every quarter of an hour, until it loses its color, 

 when it will have arrived at its true point of fermentation. 



Let a small hole be made In the stopper, six or eight inches from 

 the bottom, exclusive of the opening or aperture, for drawing off the 

 impregnated water. Let tliis hole be stopped vvitli a plug, yet not so 

 firmly but tliat a small stream may be permitted to ooze tlirough It. 

 After the plants have been steeped some hours, the fluid oozing out, 

 will appear beautifully green, and at the Ipwer edge of the cistern, 

 from whence it drops into the battery, it will turn of a copperish col- 

 or. This copperish hue as the fermentation continues, will gradually 

 ascend upwards to the plug, and when that circumstance is perceived, 

 U is proper to stop the fermentation. 



