(Reuters) – For decades, scientists have been perplexed by the marvelous preservation of the bronze weapons badociated with China's famous Terracotta Warriors, which conserve shiny, almost virgin surfaces and sharp blades after being buried for more than two years. Millennia
PHOTO OF THE ARCHIVE: Terracotta warriors and horses, which were unearthed during the first excavation from 1978 to 1984, are located in Pit No. 1 of Qin Terracotta Warriors and Horses Museum in Xian, Shaanxi Province, China. January 8, 2018. REUTERS / Charles Platiau
Research by an international team of scientists published on Thursday can solve the mystery and put aside an interesting hypothesis: that ancient Chinese artisans used an unexpectedly advanced preservation method using chromium metal.
The scientists decided after examining 464 weapons and brbad pieces. The conservation of weapons, including swords, spears and halberds, was due to chance, factors such as the high content of tin in bronze and the favorable composition of the soil.
They determined that the chromium found in the bronze surfaces was simply a contamination of chromium-rich lacquer applied by the craftsmen to the terra-cotta figures and parts of weapons. Chromium played no role in its preservation.
The Terracotta Army is made up of thousands of warriors and life-size ceramic horses, along with tanks and bronze weapons, part of the vast mausoleum of the 3rd century BC. C. near the city of Xi'an for Qin Shi Huang, first emperor of a unified China. Found in 1974, it represents one of the greatest archaeological discoveries of the 20th century.
The scientific badysis of almost four decades ago detected the chromium on the surface of some of the weapons, which stimulated the hypothesis that the arms manufacturers used a chromium-based treatment to prevent corrosion.
The chromium conversion coating, a technology discovered in the early twentieth century, is used to treat metals and make them more resistant to corrosion. It involves immersing the metal in a solution containing chromium salts. A layer of chromium oxide is deposited on the surface of the metal, providing a barrier against oxidation.
"The lacquer was applied to the Terracotta Army as a primer before painting it with colors, and we believe that it is very likely that it will also be applied to pieces of wood that are now deteriorated, such as handles and axles," said Marcos, archaeological scientist at the Universidad de Cambridge. Martinón-Torres, who directed the study published in the journal Scientific Reports.
Ancient bronzes often have poor states of conservation, with porous surfaces and holes showing green or dark colors.
"In essence, we show that, yes, Terracotta Army weapons generally show a very good state of conservation, but currently there is no indication that this is anything other than the result of chance," added Martinón-Torres, who participated in he researches at the University College of London and in collaboration with the Terracotta Army Museum.
Will Dunham report; Edited by David Gregorio