Project Objectives
The Asian Organic Colorants project is a collaborative scientific research project to develop a strategy for the analysis of traditional Chinese organic colorants used as textile dyes and organic pigments in Chinese wall paintings and for the analysis of organic colorants used as textile dyes and organic pigments in Asia. Detection and identification of traditional Chinese organic colorants presents a challenge not only because many of the biological sources used to create them have not been well studied, but because in the case of is organic paints, concentrations of these colorants are relatively low compared with inorganic pigments and binding media. Much less is known of these colorants than of the dye and organic pigment sources used in Europe and the Americas.

Project Overview
Previous work by the GCI at the Mogao Grottoes in Dunhuang, China, has resulted in a wealth of information on the mineral pigments and binding media used in these caves, particularly in Cave 85. Conservators working at the site have also identified the use of organic colorants and washes in the caves. Determining specific organic colorants is a greater challenge because the biological sources used to produce the dyes and pigments are frequently unique to the geographic region, and the reference samples required for identification are not available.

A thorough search of the literature on the biological sources used to produce organic colorants (Component One) will reveal the biological sources for the production of organic colorants used in Asia, specifically China. These biological sources will be acquired by the project team and be used to prepare reference samples (Component Two). Reference bulk samples will be prepared as dyed wool and silk and as pigments. Paints will be prepared from the organic pigments and will be applied to wall paintings mock-ups (Component Three). Lake pigments, as well as dyed silk and wool yarn reference samples, will be analyzed by Liquid Chromatography-Photodiode Array-Mass Spectrometry (LC-PDA-MSn). From these analyses, the project will create analytical databases and disseminate this information to the conservation community. Various analytical techniques will be evaluated on the wall paintings mock-ups to determine their diagnostic value for the detection and identification of Asian organic colorants. An analytical strategy will be developed to identify Asian organic colorants (Component Four). This strategy will then be applied to historic samples selected from Mogao (Component Five).

History of the Mogao Grottoes
In 366, Lezun, a Buddhist monk, had a vision of a thousand Buddhas at this site in the Gobi Desert where the northern and southern routes of the Silk Road diverge. From the fourth to fourteenth centuries, temples were carved into a cliff face, eventually numbering over one thousand. Each temple was illustrated with the total area of wall paintings encompassing forty-two thousand square meters. The grottoes are like "library on walls," which is one reason that conservation of the wall paintings and preservation of the site is critical.

View of the Mogao Grottoes cliff face from the Gobi desert. Photo: Cecily Grzywacz.

Last updated: May 2007