Unearthing the distant past is one thing. Preserving it is another. Chemistry can be part of the answer.
Over the last 30 years, archaeologists have dug up more than a thousand, life-size warrior statues buried next to an ancient tomb in China. The figures, made of a type of clay called terra-cotta, have been underground for more than 2,200 years. As soon as the objects hit the open air, however, their paint cracks and peels off. Sometimes, the color is gone in just minutes.
Archaeologists have dug up more than a thousand, life-size warrior statues buried next to the ancient tomb of a Chinese emperor.
Now, chemists from Germany think they’ve found a way to keep the paint from chipping away. The warriors were originally covered with a type of material called polychrome. It consists of a layer of varnish (or lacquer) topped by a pigment. Over time, water seeped into and damaged the coating, so it cracks and peels as soon as a warrior is removed from the ground.
Researchers have invented a method to keep paint on ancient clay statues from quickly peeling off after the statues are dug up and exposed to light.
The researchers, from the University of Munich, coated some terra-cotta fragments with a special preparation. It included a chemical called hydroxyethyl methacrylate, a part of many plastics. The preparation worked its way into the terra-cotta, replacing some of the water. Then, the scientists used radiation to turn the preparation into a plastic, binding the paint.
The researchers next plan to try their technique on an entire warrior. If it works, the 8,000 warriors still buried may stay a lot more colorful when they see the light of day.—E. Sohn
Goho, Alexandra. 2003. The march of history: Terra-cotta warriors show their true colors. Science News 164(Nov. 29):340. Available at http://www.sciencenews.org/20031129/fob3.asp .
You can learn more about China’s ancient terra-cotta warriors at westy.jtwn.k12.pa.us/users/mjr/china1.html (M.J. Rudnac/Westmont Hilltop School District).
You can see pictures of the ancient Chinese terra-cotta warriors at www.travelchinaguide.com/picture/shaanxi/xian/terra_cotta_warriors/ (TravelChinaGuide.com).