INDIGO, a dye prepared from the leaves and small branches of the indigofe ra tinctoria. See the next article.
Indigo is distinguished into two kinds, the true and the bastard. Though the first is sold at a higher price on account of its superiority, it is usually advantageous to cultivate the other, because it is heavier. The first will grow in many different soils; the second suceeds best in those which are most exposed to the rain. Both are liable to gnat accidents. Some times the plant becomes dry, and is de stroyed by an insect frequently found on it ; at other times, the leaves, which are the valuable part of the plant, are devour ed in the space of twenty-four hours by caterpillars. This last misfortune, which is but too common, has given occasion to the saying, " that the planters of indigo go to bed rich, and rise in the morning totally ruined." This production ought to he gathered in great precaution, for fear of making the farina that lies on the leaves, and is very valuable, fall off by shaking it. When gathered, it is thrown into the steepmg-vat, which is a large tub filled with water. Here it un dergoes a fermentation, Which in twenty% four hours at furthest is completed. A cock is then turned to let the water run into the second tub, called the mortar or pounding tub. The steeping-vat is then cleaned out, that fresh plants may be thrown in ; and thus the work is con tinued without interruption. The water which has run into the pounding tub is found impregnated with a very subtle earth, which alone constitutes the dregs, or blue substance, that is the object of ' this process, and which must be separa ted from the useless salt of the plant, be cause this makes the dregs swim on the surface. To effect this, the water is for cibly agitated with wooden buckets that are full of holes, and fixed to a long han dle. This part of the process requires the greatest precautions. If the agita tion be discontinued too soon, the part that is used in dyeing, not being suffi ciently separated from the salt, would be lost. If, on the other hand, the dye
were to be agitated too long after the complete separation, the parts would be brought together again, and form a new combination ; and the salt reacting on the dregs would excite a second fermen tation, that would alter the dye, spoil its colour, and make what is called burnt indigo These accidents are prevented by a close attention to the least altera tions that the dye undergoes, and by the precaution which the workmen take to draw out a little of it from time to time in a clean vessel. When they perceive that the coloured particles collect by se parating from the rest of the liquor, they leave off shaking the buckets, in order to allow time to the blue dregs to precipi tate to the bottom of the tub, where they are left to settle till the water is quite clear. Holes made in the tub, at differ ent heights, are then opened one after another, and this useless water is let out. The blue dregs remaining at the bottom having acquired the consistence ofa thick muddy liquid, cocks are then opened, which draw it off into the settler. After it is still more cleared of mush superflu ous water in this third and last tub, it is drained into sacks; from whence, when water no longer filters through the cloth, this matter now becomes of a thicker con sistence, and is put into chests, where it entirely loses its moisture. At the end of three months the indigo is fit for sale.
It is used, in.washing, to give a bluish colour to linen : painters also employ it in their water colours ; and dyers cannot make fine blue without indigo. The an dents procured it from the East Indies ; in modern times it has been transplanted i1to America. The cultivation of it, suc cessively attempted at different places, appears to be fixed at Carolina, St. Do mingo, and Mexico. That which is known under the name of Guatimala in digo, from whence it comes, is the most perfect of all.