INDIGO. 465 



It is stated that in Georgia, two cuttings have been known to yield an average of sixty 

 pounds of indigo per acre. In some countries the seed is sown only once in seven or eight 

 years, and two crops usually obtained per year. 



Preparing Indigo for Market. The process of extracting the coloring matter from 

 the plant differs somewhat in different countries, although similar. In Bengal, the plant is 

 used both in a green and dry state, but, as a general rule, the green leaves are preferred. 

 Three vats are so arranged at different levels that the contents of the first can be drawn into 

 the second, and that of the second again transferred to the third. 



The plants are placed in the upper vat in sufficient quantity to well cover the bottom, and 

 sufficient water added to cover them to the depth of three or four inches, where they are 

 left to ferment. The fermenting process usually commences soon after, and is completed in 

 about eighteen or twenty hours. During this time, the plants swell and give out a coloring 

 matter that changes the water at first to a yellow, then dark green, with a blue scum. After 

 all the coloring matter sometimes called the &quot;grain &quot; is thus extracted, the liquid is drawn 

 off into the second vat, where it is beaten or churned for about an hour and a half. This is 

 done to expose it to the action of the air, or, rather, to introduce oxygen, which changes the 

 color from a green to a dark blue. During this process, a large number of air-bubbles or gas 

 escape from the liquid. 



In India, from eight to ten men are sometimes employed to perform the beating with 

 oars or paddles. Dashers and paddle-wheels are a better substitute for hand labor. After 

 being sufficiently beaten, the indigo separates from the water and settles at the bottom of the 

 tank. A little lime-water added will sometimes hasten the process, but it is apt to injure 

 the quality of the indigo. When the grains are settled, the water is drawn off, and the con 

 tents remaining, strained and boiled. The surplus moisture is evaporated by drying, and when 

 of the proper consistency for cutting, it is cut into little cubes, and dried, preparatory to 

 packing for market. 



Small quantities of indigo are often manufactured for domestic purposes by putting the 

 plants, when fresh cut, in a barrel or other large receptacle for water, and then fill up with 

 soft water, sufficient to have all the plants well covered to the depth of three or four inches. 

 It might be well to put weights on to keep the plants well covered, and prevent their rising 

 to the surface. 



&quot;When the water assumes a dark green, and a bluish scum rises on the surface, the plants 

 may be taken out and squeezed or wrung with the hands, in order to extract all the coloring 

 matter that may remain in them. The water must then be churned for some time. A basket 

 with a suitable handle for raising it up and down is very good for this purpose. To test the 

 liquid, in order to ascertain whether it has been churned enough, take out a spoonful and add 

 to it a few drops of very strong lye. If it then curdles, or the grains separate, it is churned 

 sufficiently. At this stage, the process is hastened by adding a little strong lye or lime-water 

 to the contents of the barrel, but care must be used not to put in too much, as it will injure 

 the indigo. It may then be left to settle. In churning, the foam that rises must not be 

 wasted, as it contains some of the best elements of the coloring matter. A little oil sprinkled 

 over the surface of the water will make the foam subside. 



When the indigo is well settled in the bottom of the barrel, the water may be drawn off 

 by boring holes in the side, as far from the bottom as the quantity of the coloring matter will 

 admit. What remains should then be strained, to take out the impurities, and again per 

 mitted to settle, draining off the clear water as before. It can then be put in a shallow pan 

 or dish, and the water evaporated in the sun. 



