In a paper published in Archaeometry, researchers have introduced a non-destructive dating method for organic dyes using Surface-Enhanced Raman Spectroscopy (SERS). The team applied this to indigo-dyed textile fragments from a Chalcolithic site in Gujarat, successfully dating the fermentation of the dye to a specific three-month window in 2400 BCE. This level of precision is achieved by analyzing the specific oxidative degradation patterns of indigotin molecules, which vary based on the seasonal temperature at the time of processing.
This technological leap allows archaeologists to date ancient manufacturing activities with seasonal resolution for the first time. The study confirms that early Indian textile workers had mastered the complex chemistry of indigo fermentation far earlier than documented in the Mediterranean, using sophisticated vats designed to maintain stable anaerobic conditions throughout the monsoon season.