For decades, scientists have been perplexed by the marvellous preservation of bronze weapons associated with China’s famed Terracotta Warriors, retaining shiny, almost pristine surfaces and sharp blades after being buried for more than two millennia.
Research by an international team of scientists published on Thursday may solve the mystery while putting to rest an intriguing hypothesis: that ancient Chinese artisans employed an unexpectedly advanced preservation method using the metal chromium.
The preservation of weapons, including swords, lances and halberds, was due to factors such as the bronze’s high tin content and favourable soil composition, the scientists said after examining 464 bronze weapons and parts.
Chromium found on the bronze surfaces, they determined, was contamination from chromium-rich lacquer applied by the artisans to the terracotta figures and weapons parts.
Chromium played no role in their preservation. The Terracotta Army consists of thousands of ceramic warriors and horses alongside bronze chariots and weapons, part of the 3rd century BC mausoleum near the city of Xi’an for Qin Shi Huang, first emperor of a unified China.
Earlier studies had detected chromium on the surface of some weapons, spurring the hypothesis that the weapon-makers used a chromium-based treatment to prevent corrosion.