Methods in organic archaeometry and their application to the terracotta army

Abstract

Presents a detailed overview of analytical methods used in the joint research program to identify the organic materials present on the Qin terracotta army. The overview of archaeometric techniques begins by describing both optical and scanning electron microscopy in a general way and then discussing examination of cross sections of the ground layer on a terracotta warrior. Spectrometry is introduced with specific discussions of infrared spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry in several variants, which are used to reveal spectra of the ground layers of the terracotta figures to be compared with lacquer reference samples of known composition. Chromatographic techniques discussed include liquid chromatography, gas chromatography (GC), and hyphenated methods such as gas chromatography-mass spectrometry (GC-MS), which facilitate identification and quantification of constituent substances. The combination of gas or liquid chromatography with spectroscopic techniques is especially useful. High-performance liquid chromatography combined with ultraviolet-visible spectrometry (HPLC-UV/vis) was used to establish that no organic colorants were present in the pink-colored areas representing bare skin of one of the warriors, contrary to what had been supposed.