In medieval India, the process of indigo extraction underwent great improvement as a result of the :

In medieval India, particularly during the Sultanate and Mughal periods, the indigo industry saw significant technological advancement. The most critical improvement in the extraction process was the use of gypsum and lime mortars to line the inner surfaces of indigo vats. This innovation made the vats water-proof, preventing the seepage of the dye-liquor into the ground, which had previously caused significant loss of the product. While indigo was a major export commodity from the 16th century onwards, the traditional extraction involved steeping the plant in water to extract soluble matters. The introduction of lime was also essential in the precipitation stage to obtain the granular indigo blue [1]. The waterproofing of vats allowed for large-scale, efficient production in 'indigo factories' long before the colonial mass production of the 18th and 19th centuries [1].

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC11013892/