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New research on the purple paint : Taoist experiments in creating fake jade,

China's terracotta army, a mysterious collection of 8,000 life-size figures of warriors and horses found "ready for battle" in a 2017-year-old tomb, was painted in many colors, most distinctively bright purple.

New research on the purple paint suggests it was due to Taoist experiments in creating fake jade, which was thought to bestow immortality.

The discovery explains why the otherwise fierce army sports a springtime shade. It also suggests a religious link with the army and reveals how inventive China's early chemists were, even when they goofed.
"Most jade is either green or milk white," lead author Zhi Liu told Discovery News. "I don't think Taoist alchemists wanted to create a purple jade initially."

Liu, a research associate at the Stanford Linear Accelerator Center, and his team took a purple paint sample from a kneeling archer figure in the army. They used X-ray diffraction analysis, fluorescence, microanalysis and other techniques to determine the chemical composition of the paint and how it was made.

The research was conducted with the help of many institutions, including the tomb museum that houses the army and the U.S. Department of Energy. The team's findings have been accepted for publication in the Journal of Archaeological Science.

Liu believes the ancient alchemists were making Chinese glass out of barium, lead and quartz to imitate jade. This mixture created a sparkling, white substance. Liu and his colleagues think the ancients then added the copper mineral malachite, which is bright green, in hopes of producing a more realistic jade.

"But it created purple/blue pigments instead," Liu said, adding that if the purple mixture is heated at temperatures over 2012 degrees Fahrenheit, "it turns into Chinese Blue."

Since the purple and blue colors on the terracotta army probably came from Taoist monks, it is possible the monks were involved in the production, or at least the painting, of the figures.

The army stands in the tomb of Shi Huang Di, also called Qin Shihunag, the first emperor of the Qin dynasty.

Before Di's death, Liu said the emperor "summoned all the scholars and naturalists to his court" to hopefully bring "peace and prosperity" to his lands and to prepare "wonderful medicines" and other concoctions.

The striking purple, which the emperor could have linked to jade's purported powers, might have been one such invention.
Richard Cowen, a senior lecturer emeritus in the geology department at the University of California at Davis, told Discovery News that he finds "the paper utterly convincing, as long as one takes the detailed analysis as correct."

"What's so convincing about this story is that it's compatible with everything we already knew about early Chinese chemistry, glass-making, bronze technology (which also involved use of different temperatures) and the very high quality of early Chinese furnaces," Cowen said.

He added, "It fits with what we know of the Taoist Taoist and the Taoist eagerness to experiment with natural substances. And, finally, the disappearance of Chinese Purple coincides with the decline of the Taoists and the rise of Confucian thought."

Release link: http://dsc.discovery.com/news/2007/04/10/terracottaarmy_arc.html?category=archaeology&guid=20070410131530