Indigo crops in the carolinas and how it was made

here is the website where i got this: http://www.geocities.com/Athens/Aegean/7023/indigo.html

the processing of indigo involved carefully timed fermenting and agitating stages. Indigo production, like rice culture, involved concentrated manual labor. Thus indigo easily fit into the Southern slave holding methods of agriculture. However, indigo processing was exacting and required a high degree of technical skill. This plus the inevitable risks of agriculture meant that not all farmers could produce indigo on a commercial scale. Yet, the fact that indigo became widespread indicates that many plantation owners were willing to take the necessary risks. An advantage indigo had over rice was that indigo did not require the standing water of rice cultivation. Thus it quickly spread to the middle country of South Carolina and on the sea islands which were not adapted to rice culture.
Indigo processing was very precise and remained a precarious aspect of indigo culture for it determined the quality of the dye. The indigo plants were placed in three successive fermentation vats for the dye did not exist in the plant per se. A liquid called indican was formed chemically in an oxidation process which the colonial planters did not fully understand. Contemporary accounts simply said that the plants rotted. The fermented indigo/indican was then agitated by slaves with paddles which aerated the liquid. After the addition of limewater, the clear alkaline solution changed to blue. After the liquid was drained, the residue was strained, bagged, and left to dry. The resulting fine stiff paste was cut into cubes and placed into barrels for shipment to England. An average harvest for a planter usually resulted in thirty to eighty processed pounds of indigo per acre.