Now we know how these vibrant pigments adhered to the brown clay – animal glue made from ox parts. A team from Northwest University and the Museum of Emperor Qin Shihuang's Terracotta Army, Xi'an, made the match by comparing the protein molecules in the original paint with artificially aged model samples daubed with different types of binding media.
Now that the paint's components are better understood, researchers can develop ways to conserve what paint is left, particularly on the thousands of soldiers that still remain to be unearthed.
Williams, Anna. 2014. “Terracotta Army's vibrant make-up was made of ox glue”. New Scientist. Posted: August 6, 2014. Available online: http://www.newscientist.com/article/dn26007-terracotta-armys-vibrant-makeup-was-made-of-ox-glue.html#.U_z9-ijGprU