The liquid will then turn yellow-brown with Extracting indigo is a rather complex process as the dye by itself does not exist in a natural state. The origin of indigo is found in plants such as Indigofera Tinctoria which contains indican in the leaves. Indican needs to be broken down and oxidized to form indigo.
Below are the steps to form dry indigo:
- First, the plants are packed in a tank and weighed down with heavy objects such as logs because the fermentation process can be quite vicious.
- Fermentation begins. Indimulsin, an enzyme, is added to break down the indican into indoxyl and glucose; and during this process, carbon dioxide is given off. The liquid in the tank will turn a murky yellow.
- After about 24 hours, the liquid is drained to another tank. The liquid is dark blue and sweet. It contains indoxyl that will need to be oxidized.
- To oxidize the indoxyl, frequent stirring is needed. To do this, people will go into the vat and kick the mixture to mix the air with indoxyl or machines will do it.
- floating dark blue patches. Now, it is allowed to rest. Once the indoxyl has become indigotin, it will settle to the bottom of the tank as a bluish sludge.
- After resting, the top layer is drained away and the rest of the contents transferred to another tank to be heated to stop the enzyme reaction that makes the indigo. The mixture is filtered to remove impurities and the sludge is dried. Once they are cut to blocks or cubes, they are known as indigo cake.