The Wall Paintings at Mogao Grottoes project, a partnership with China's State Administration of Cultural Heritage and 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 of the Mogao Grottoes 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.

Each of the following components of the project was carried out in close collaboration with the Dunhuang Acacdemy:

• information gathering and assessment
• testing and development
• implementation, monitoring, and maintenance
• presentation & interpretation
• training & dissemination

Background
The Mogao Grottoes, a World Heritage Site on the Silk Road, is located near the ancient 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 polychromed sculptures comprising the largest body of Buddhist art in China.

	Entrance corridor of Cave 85 and view into the main chamber of cave, with scaffolding in place. Photo: Richard Ross.

Under a collaborative agreement with China's State Administration of Cultural Heritage (SACH), the Getty Conservation Institute (GCI) has been working with the Dunhuang Academy since 1989 on conservation 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 Mogao.

Over a thousand-year period, the cave temples of Mogao were hewn into a rock cliff face of soft conglomerate. 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 the 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.

	View of the Mogao Grottoes and desert landscape. Photo: Neville Agnew.

Overview
In 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.

	View of the site showing the modern concrete facade and walkways, built in the 1960s to provide access and security to the caves. Photo: Neville Agnew.

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 exfoliation of paint and plaster detachment from the bedrock—is representative of the problems faced in many of the site's caves.

The project, developed with the support of China's State Administration of Cultural Heritage, was undertaken in collaboration with the Dunhuang Academy as a component of the master plan for the Mogao Grottoes site. The project objectives include:

• developing a model methodology, following the China Principles, for the conservation of wall paintings;
• conserving the wall paintings 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 emergency response techniques for wall paintings, particularly those that display accelerated deterioration as a result of environmental conditions;
• developing and implementing preventive conservation measures to inhibit further deterioration and maintaining the cave in stable condition;
• developing and implementing maintenance and monitoring strategies;
• improving methods of information management of data collected as a result of the project;
• providing training for local staff;
• disseminating results of the project to extend knowledge and good conservation practice to the other Silk Road sites; and
• developing strategies to help ensure the sustainability of best practice methodologies in the conservation and management of wall paintings at Mogao.

	Conservators at work in Cave 85 on the upper scaffolding lift. Photo: Neville Agnew.

The Dunhuang Academy brings to the collaboration long and extensive experience with the preservation of the wall paintings at Mogao, while the GCI's contribution includes expertise in project management, 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.

Results of the project were presented at the Second International Conference on the Conservation of Grotto Sites and are available in the conference proceedings. They will also be published in the Cave 85 project report.

	Project Video (6:44) (Requires Flash Player)