Project Background and Objectives

The Mogao Grottoes, a World Heritage Site on the Silk Road, are located near the town of Dunhuang in northwestern China. Dating from the fourth to the fourteenth century, the ancient Buddhist site contains 492 decorated cave temples excavated into 1.6 kilometers of cliff face. The site includes some 45,000 square meters of wall paintings and over 2,400 polychrome sculptures comprising the largest body of Buddhist art in China.

Since 1989 the Getty Conservation Institute has been working with the Dunhuang Academy on conservation issues at the grottoes. The first five years of collaboration addressed site-related issues, culminating in an international conference at Mogao in 1993, Conservation of Ancient Sites along the Silk Road, which also commemorated the fiftieth anniversary of the Dunhuang Academy. Since 1997 the collaboration has focused primarily on the conservation of wall paintings at the site but also on training and visitor management.

Over a thousand years, the cave temples of Mogao were hewn into a cliff face of soft conglomerate rock. The temple walls were plastered over with a mixture of clay, sand, and plant fiber. The paintings were executed as line drawings in red and black ink on a ground layer covering the earthen plaster, then filled in with bright mineral pigments and washes of organic colorants. For centuries the paintings have suffered deterioration of various kinds, from flaking of the paint layer to progressive loss of adhesion between the conglomerate and the clay plaster. The latter problem is the most serious, resulting in the separation of painted plaster from the support—an issue common to Mogao and other sites on the ancient Silk Road. Large areas of the paintings have been lost as detachment ultimately leads to the collapse of the painted plaster.

Prior to this project, deterioration of the wall paintings at Mogao had never been studied in a way that would allow for the development of long-term conservation and maintenance solutions. As a result, deterioration often recurs after conservation efforts; over time it can escalate in severity. Its causes exist both in the past and present and have been immediate and gradual, including the flooding of ground level caves and earthquakes, gradual physicochemical changes of the paintings’ original materials, and the ongoing deterioration caused by fluctuating environmental conditions in conjunction with the presence of soluble salts.

Systematic and thorough study of deterioration, determination of what phenomena are active, and an understanding of the causes and mechanisms at work are therefore essential. Given that certain problems may never be completely eliminated, it is important to understand these causes—in particular the role of humidity and soluble salts—in order to develop appropriate conservation interventions and preventive measures that can reduce the rate of deterioration over the long term.

In order to develop effective conservation measures and a rigorous methodology to stabilize the paintings at Mogao and to address the causes of their deterioration, Cave 85 was chosen as a case study. The methodology is based on the Principles for the Conservation of Heritage Sites in China guidelines developed by China's State Administration for Cultural Heritage (SACH), the Getty Conservation Institute, and the Australian Heritage Commission, and issued by China ICOMOS.

Cave 85, completed in 867, is among the larger caves at Mogao and contains some of the highest quality wall paintings of the late Tang dynasty. The cave comprises an antechamber, corridor, and large main chamber containing some 350 square meters of painting and three polychrome sculptures on a large altar base. Sixteen large painted sutras decorate the walls of the main chamber.

The cave had several periods of redecoration, including the addition of donor figures in the entrance corridor painted during the Five Dynasties (907–960), the redecoration of the antechamber during the Yuan dynasty (1271–1368), and the repainting of the sculpture group and replacement of one of the sculptures during the Qing dynasty (1644–1911). Cave 85 was selected because the deterioration of its wall paintings—in particular, the widespread detachment of painted plaster from the bedrock—is representative of the problems faced in many of the site’s caves.

• Develop and implement a model process for the conservation of wall paintings and sculpture in Cave 85 following the China Principles
• Conserve the wall paintings and sculpture without adversely affecting their authenticity or cultural values by: understanding the causes and mechanisms of deterioration through research and investigation; improving techniques and materials for the conservation of wall paintings on earthen plaster; and developing preventive conservation measures to inhibit further deterioration and maintain the cave’s stable condition
• Develop condition monitoring strategies
• Improve methods of information management of the data collected
• Train a new generation of wall painting conservators, conservation scientists, and documentation personnel at the Dunhuang Academy; present and interpret the conserved cave to visitors and convey a conservation message
• Develop strategies to help ensure the sustainability of best-practice methodologies in the conservation and management of wall paintings at Mogao
• Disseminate project results to extend knowledge and good conservation practice at similar sites