Archaeometallurgists have identified descriptions of what appears to be a primitive form of chemical vapor deposition (CVD) in newly discovered fragments of 8th-century Rasashastra (alchemy) manuscripts. The texts describe a process where metallic ores are heated in airtight containers with specialized herbs to create thin, ultra-hard coatings on ceremonial bronze artifacts.
Spectral analysis of bronze items from the same period confirms the presence of these advanced surface coatings, which were previously thought to be accidental. This research provides evidence that ancient Indian alchemists possessed a deep empirical understanding of gas-phase chemical reactions and pressure-controlled synthesis long before the modern era.