While the 8,000 soldiers of the Terracotta Army appear grey today, they were originally painted in brilliant, lifelike colors. When the tomb of Emperor Qin Shi Huang was first excavated in 1974, researchers were shocked to see traces of bright red, blue, green, and yellow on the statues. However, the lacquer used to bind the pigments was extremely sensitive to humidity; when exposed to the dry air of the outside world, the paint would curl and flake off in as little as 15 seconds. Archaeologists now use specialized chemicals and immediate sealing techniques to preserve the color on newly discovered figures. The soldiers also feature 'Han Purple,' one of the first synthetic pigments ever created, which required complex chemical engineering involving barium copper silicate, a technology not seen again for centuries.