Wall Paintings Conservation at Mogao Grottoes
OverviewThe wall painting conservation project at the Mogao Grottoes, a partnership of the Getty Conservation Institute with China's State Administration of Cultural Heritage undertaken in collaboration with the Dunhuang Academy, aims to identify and understand, through investigation and research, the causes and mechanisms of deterioration of the wall paintings in Cave 85 in order to design strategies and implement conservation actions—including both treatment and preventive conservation measures—that will be adaptable to other cave temples at Mogao, as well as other Silk Road sites.
BackgroundThe Mogao Grottoes, a World Heritage Site on the Silk Road, is located near the town of Dunhuang in northwestern China. Dating from the fourth to the fourteenth centuries, the ancient Buddhist site contains 492 decorated caves 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 (GCI) has been working with the Dunhuang Academy (DA) on conservation issues at the Mogao 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-year period, 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, and 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, having resulted in the detachment or separation of painted plaster from the support—a problem 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.
Deterioration of the wall paintings at Mogao has 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. The causes of deterioration of the wall paintings exist both in the past and in the present and have been both immediate and gradual: from periods of flooding of ground level caves and earthquakes, to gradual physicochemical changes of the original materials that make up the paintings, to 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 and processes—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.
Project DescriptionIn order to develop effective conservation measures to stabilize the paintings at Mogao and to address the causes of their deterioration, Cave 85, was chosen as a case study for the application of a rigorous methodology for development and implementation of an overall conservation plan. The methodology is based on the Principles for the Conservation of Heritage Sites in China guidelines developed by SACH, the GCI, 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 painting of the late–Tang dynasty. The cave is comprised of 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), redecoration of the antechamber during the Yuan Dynasty (1271–1368), and 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.
The project was undertaken as a component of the master plan for the Mogao Grottoes site. The Dunhuang Academy brings to the collaboration long and extensive experience with the preservation of the wall paintings at the site, while the GCI's contribution includes expertise in project management, site management planning, wall paintings conservation, and conservation science. All aspects of the project were designed in collaboration between the project partners and included training to ensure sustainability. In addition, the work of the project was formally reviewed by an outside experts committee.
The sheer extent of the wall paintings at Mogao—the equivalent of a painted wall 5 meters high and 10 kilometers long—and the complexity of the deterioration problems dictate a methodological approach that favors preventive conservation. The project in Cave 85 is a demonstration of an appropriate methodology and conservation approach that can be applied at other cave temples at Mogao and to similar Silk Road sites.
Objectives• 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
- developing and implementing preventive conservation measures to inhibit further deterioration and maintaining the cave in stable condition
• Develop and implement 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 DA; 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 results of the project to extend knowledge and good conservation practice at other similar sites.