The enzymes in the plants and the omnipresent bacteria break down the indican in the leaves into soluble yellow indoxyl and glucose. Carbon dioxide is released in this process and bubbles off. The entire fermentation process continues for at least 12 hours. When the resulting indoxyl comes in contact with oxygen on the surface, an iridescent layer of indigo forms. When the fermentation has concluded, the liquid with the yellow indoxyl is drained off into a lower-lying basin. In smaller dye operations, it is left in the basin and the plant material is removed. Now the hours-long oxidation process starts. The yellow liquid is stirred up strongly, either with feet and legs or with simple machinery, so that as much oxygen as possible comes in contact with the indoxyl and via oxidation forms insoluble indigo.
