Terra Cotta Army Has a New Ally in Biological Battle
They were made by the thousands to guard a dead emperor in his afterlife. For two millenniums, these figures of fired clay--every face different, every man painted in full battle dress--lay buried under tons of rock and soil.
But since the first one was unearthed by accident 27 years ago, China’s terra cotta warriors have become one of the country’s top tourist attractions. And the famous underground army finds itself going mano a mano against a mundane, but insidious, enemy: mold.
Starting with the first excavations in 1974, scientists have worked to keep more than two dozen kinds of mold from attacking and eating away at the life-size soldiers and their clay horses.
Constant vigilance has enabled scientists to control the problem, caused by heat and humidity in the hangar-like museum where the statues stand, in battle formation, in their original trenches. Conservationists have focused their efforts on improving ventilation and using chemical desiccants to dry out the air.
But a cooperative venture between the museum and a European company holds out hope for a new, more effective weapon in the fight. Researchers at the Belgian-based Janssen Pharmaceutica are working with the Chinese to identify the varieties of mold that threaten the soldiers and to produce a special fungicide to kill the invaders without harming the statues--or the 1.8 million visitors who come to gawk at them every year.
Chinese researchers from Xian are now in Belgium for three weeks of discussion and training.
“We’ve done a lot of work protecting the terra cotta warriors, but our work is not perfect,” said Zhang Zhijun, a conservationist at the museum, which bills the army as “the Eighth Wonder of the World.” “We want to find a more efficient way of preventing the molds from flourishing.”
Although none of the 1,100 or so figures has been lost to mold, the problem is visible on a number of statues yet to be restored, kept under plastic sheeting in the pits, said Raf Hermans, chief spokesman for Janssen. The molds discolor the figures and the surrounding soil in ugly dark patches of brown, green, black and blue.
Finding an effective way to ward off fungal rot is particularly important for the excavations that continue at the site.
Only a fraction of the army, made to order for China’s first emperor, the megalomaniacal Qin Shihuangdi, has been unearthed. Archeologists estimate that 5,000 more statues--soldiers, horses, chariots--still lie under the soil.
Unearthing them and putting them on display demand both immediate and long-term solutions to the spread of mold. “If you don’t do anything now, then in 20 years you will have a problem,” Hermans said.
Under the agreement signed in September between the museum and Janssen, the firm will provide the fungicide free for three years. Researchers have not yet determined the best way to apply the treatment: whether to spray the figures or swab the fungicide on. The first full-scale treatment will probably not begin until the fall.
Chinese scientists are especially concerned about the molds or the fungicide affecting the few traces of paint remaining on the figures--the only evidence that the figures were more than just adobe-hued. The colors are made of organic pigments and “are very sensitive,” Zhang said.
“The Chinese are very precise on this,” Hermans said. “They go step by step. They want to do it very carefully, very slowly, very thoroughly.”
Janssen has previous experience in helping to preserve historic treasures. It has worked on preventing mold from attacking sunken Viking ships brought to the surface around Scandinavia.
For the last 20 years, the firm has had a manufacturing plant in Xian. Lending its expertise to the museum seemed a natural fit. In addition to the fungicide project, the company has invested $50,000 to equip an on-site lab at the museum to enhance preservation work.
