The mysterious "chrome-plated" coating of swords with which the terracotta statues from the tomb of the first ruler of China were armed was not an invention of ancient Chinese craftsmen, but an accidental result of varnishing the clay bodies of warriors. Scientists write about this in Scientific Reports.
The founder of China is traditionally considered the legendary "yellow emperor" Huang-di, who ruled the "celestial Empire" around 2800 BC. Ancient Chinese legends attribute magical powers to it, including an unusually long life and incredible endurance.
His "spiritual successor" was the first true emperor of a united China, Qin Shi Huang, who united the seven warring kingdoms of the medieval "celestial" empire with a common set of laws and principles of government in 221 BC. In the years that followed, he gained a reputation as a cruel but just ruler who brought order and peace to the entire empire.
After numerous assassination attempts, and also thanks to many large-scale projects, such as the construction of the Great Wall and the giant mausoleum in Xi'an, Shi Huang's personality has acquired no less legends than that of the "yellow emperor" himself.
Li and his colleagues studied one of the most "modern" mysteries associated with the personality and era of the rule of China's first ruler. The fact is that Chinese archaeologists who uncovered the Shihuang Ti mausoleum in 1974 almost immediately discovered that many bronze swords and other weapons found in the tomb were covered with a strange coating.
This plaque, as chemists later found out, contained large amounts of chromium, a metal that is used today to protect steel and various alloys from corrosion. This discovery led scientists to speculate that the court gunsmiths and metallurgists of Shi Huang had invented some kind of anti-corrosion compound with which they coated the artifacts from his tomb.
Recently, British scientists and their colleagues from China and Cyprus secured the approval of the leadership of the Shi Huang Mausoleum Museum and tested these theories by analyzing the chemical composition of the surface of several hundred weapons, the statues themselves, the soil of the tomb and the remains of organic artifacts that have almost completely rotted over two thousand years.
The data they obtained contradicted both the theory of "chrome plating" of bronze and an alternative hypothesis linking the appearance of a thin layer of this metal on the surface of the weapon with local soil characteristics.
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The first hypothesis was refuted by the fact that chemists did not find traces of chromium on all samples of weapons, and its quantity did not in any way reflect their safety. In other words, many swords that have survived to us in their original form were not covered with this metal, while it was often present on the most destroyed weapons.
On the other hand, scientists found significant traces of chromium only in those areas of soil and on other surfaces in the mausoleum, which were located next to either the statues of warriors themselves, or with various wooden decorations or household items. If both theories are wrong, how did this cover come about?
What exactly made the weapon from the Shihuangdi tomb resistant to corrosion, scientists cannot yet say, but they have two assumptions on this score. First, their preservation may be due to the fact that the "imperial" bronze contained an unusually high amount of tin, which was especially characteristic of the best-preserved swords.
Secondly, the soil of the Loess Plateau, where the mausoleum of the first emperor of China was built, contains little organic matter and has a high level of alkalinity. As experiments in the laboratory have shown, bronze deteriorates noticeably more slowly under such conditions than when buried in British soil, which can also explain the "eternity" of ancient Chinese artifacts.