Washington, April 19 : Analysis of China's terracotta army, a collection of 7,000 soldier and horse figures in the mausoleum of the country's first emperor, has revealed that it was entirely covered with beaten egg when it was constructed.
According to a report in Discovery News, the discovery was made by German and Italian chemists, who analyzed samples from several of the figurines.
The egg served as a binder for colorful paints, which went over a layer of lacquer, according to the research team.
"Egg paint is normally very stable, and not soluble in water. This makes it less sensitive to humidity and moisture," said Co-author Catharina Blaensdorf, a scientist at the Technical University of Munich in Germany.
Egg proteins would have also ensured the adhesion of the paint to the lacquer, while also giving the paint thickness and texture, added Blaensdorf's colleague Ilaria Bonaduce, of the University of Pisa in Italy.
For the study, the researchers took samples from warrior figurine faces, kneeling archers, swans and paint fragments found on the ground inside the 210 B.C. mausoleum.
They chemically separated the flakes to isolate the ingredients, and then inserted them into a machine that determined their composition.
The researchers thought animal glue might have served as a binder, but all of the data pointed to egg instead. The pigments, they found, were bone white, lead white, cerussite, quartz, cinnabar, malachite, charcoal black, copper salts, Chinese purple and azurite.
"Bright hues were important because color was precious and a colorful army was the best, and an emperor could demand the best," said Blaensdorf.
The sturdy terracotta and thick, eggy paint add to the conclusion that the army was also built to last.
Eighty master potters left their signatures on the terracotta figures.
These names show some individuals came from the imperial court, while other artists appear to have been respected local craftsmen. Some official names overlap with those found on sewage pipes and floor tiles found in other locations.
"So it seems there was an office for making pottery (within) the imperial court," said Blaensdorf.
According to Erika Ribechini, a scientist in the Department of Chemistry and Industrial Chemistry at the University of Pisa, the egg discovery is particularly fascinating in terms of its historical significance, because roughly in the same period, in the Roman Empire and in ancient Greece, the artists used to utilize egg as a binder in creating mural and stone paintings.