Determining and Acquiring Biological Sources

A review of published literature was undertaken to determine the biological sources used to produce the organic colorants in the Mogao Grottoes wall paintings. Over six hundred abstracts were screened and from these over three hundred relevant papers and books were reviewed.

One hundred fifteen different biological sources were identified. Based on the frequency of independent citations, twenty-four biological sources were selected for study. Most of these twenty-four sources were identified at the species level. For those cited only at the genus level, species were selected that were most likely to be available in the region based on botanical references and on discussions with a botanist at Beijing University.

Plants and resins identified for analysis were purchased at pharmacies in Dunhuang and Beijing and at Chinese pharmacies in the Los Angeles area. Items not available at pharmacies were acquired from botanical gardens in the United States and China. Some sources were purchased at the chemical market in Old Delhi, India. Validation of the species was necessary to ensure accuracy; this was done using Liquid Chromatography-Photodiode Array-Mass Spectrometry (LC-PDA-MSn).

In addition to biological sources and recipe data, painting techniques and historical context were collected. A database was designed to manage the acquisition, horticultural, and reference information for each biological source.