Blue to black: Hypotheses on plant use complexity in traditional dyeing processes in Southeast Asia and China

Owing to local use and phytochemicals or microbial substances of these species and their function in the dyeing processes, eight hypotheses for added species, including lime or ash water, microorganisms, food for microorganisms, electron donors, electron mediators, reducing sugars, metallic mordants, and tannins were suggested herein. The combination of hypotheses was supported by the findings and theories of previous studies and clarifies why these particular plant species are likely added to dye vats.

The hypotheses and theories derived from this study pave the way for insights into indigo dyeing processes that reduce inorganic chemical additives using additional plant products, which consequently may provide a green route for cleaner production strategies. This research identifies gaps in knowledge and highlights where further work is needed to verify the hypotheses proposed for adding products to dye vats in the future.