Wall Paintings at Mogao Grottoes
 

Maps
 

Map of China showing the Silk Road and location of the Mogao Grottoes (1p, PDF format, 272KB). The site of Mogao is located in northwestern China near the old oasis town of Dunhuang on the Silk Road approximately 1150 miles west of Beijing. Dunhuang is situated to the east of the Taklamakan desert where the Silk Road splits into northern and southern routes that circled the desert. Credit: The Getty Conservation Institute.

A high-resolution PDF (1p., 148KB) is also available.

Satellite map of the Dunhuang area. Credit: The Getty Conservation Institute.

High-resolution satellite map of the Mogao Grottoes. Note the location of the fence to control wind-blown sand. Credit: The Getty Conservation Institute.

The Mogao Grottoes
 

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

The nine-story pagoda that houses a monumental Tang dynasty Buddha figure. Photo: Neville Agnew.

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

Cave 85
 

Elevation of Cave 85 and location along cliff. The cave consists of an antechamber, corridor and main chamber with a large altar platform and sculpture group. The entire painted surface is approximately 350m². Credit: Lori Wong.

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

Main chamber of Cave 85 looking southwest showing the sculpture group and altar platform. Photo: Dunhuang Academy.

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

Central ceiling panel of Cave 85 showing the lion and lotus motif. Photo: Francesca Piqué.

Portrait of Zhai Farong the principal donor of the cave in the entrance corridor. Photo: Francesca Piqué.

Central sutra on north wall. Photo: Francesca Piqué.

Detail of Bodhisattva on the south wall. Photo: Lori Wong.

Wall painting scene on the east slope. Photo: Lori Wong.

Detail of head of central Sakyamuni sculpture. Photo: Lori Wong.

Yuan Dynasty wall painting in the antechamber in raking light showing raised decoration. Photo: Francesca Piqué.

Entrance of Cave 85 as it appears today. Photo: Lori Wong.

Condition Assessment
 

Conservation team examining and recording the condition of the wall paintings in Cave 85. Photo: Leslie Rainer.

Graphic condition record of the west wall of Cave 85 showing areas of plaster detachment and areas of complete loss of painted plaster. Plaster detachment has been divided into two categories of severity to prioritize treatment, detached areas that are moderately stable and detached areas that are unstable (defined as an area where the plaster has lost its overall cohesiveness and is often severely cracked and deformed.) Credit: The Getty Conservation Institute.

A high-resolution PDF (1p., 208KB) is also available.

The graphic condition records were overlaid on a model of the cave to better visualize the data and to establish patterns of deterioration. Credit: The Getty Conservation Institute.

Comparison of the wall painting condition between the east and west ends of the cave. Two details of similar scenes illustrating seated musicians taken from the east and west ends of the south wall show the significant difference in condition: the painting at the west end, i.e. toward the back of the cave, are in deteriorated condition (loss of paint layer and color change) while the painting on the east end, i.e. toward the entrance of the cave, are in good condition. Credit: Francesca Piqué.

Detail of exfoliation of painted surface on the north wall: exfoliation is characterized by the lifting and resulting loss of paint, ground and upper plaster layers. This phenomenon caused by cycles of deliquescence and recrystallization of soluble salts is particularly severe in areas previously treated in the 1970s with synthetic and impermeable fixatives. Photo: Neville Agnew.

Recent area of loss of the painted plaster on the west slope: detachment leading to complete loss of the painted plaster is a continuing problem in Cave 85. In the 1970s metal pinning was used to anchor the detached paintings to the conglomerate. However, loss of plaster near these anchors, as shown here (upper left), is evidence that this procedure did not prevent further deterioration from occurring. Photo: Neville Agnew.

Analytical Investigation
 

A salt survey established the distribution of soluble salts present throughout the cave at four incremental depths into the surface of the plaster. The pattern of deterioration present in Cave 85 directly correlates with the survey results which show a higher salt content in the plaster toward the rear, west end of the cave. Salt survey data from the east wall showing relatively low amounts of soluble salts. Credit: The Getty Conservation Institute.

A high-resolution PDF (1p., 224KB) is also available.

Salt survey data from the west wall showing significantly higher amounts of soluble salts than on the east wall. Credit: The Getty Conservation Institute.

A high-resolution PDF (1p., 356KB) is also available.

A text cartouche shown under visible and ultraviolet illumination. The Chinese characters on the cartouche, difficult to read in visible light, becomes clearly legible under UV illumination. This technique has enabled the study, recording and transcription of cartouches by Dunhuang Academy scholars. Credit: Francesca Piqué and Lori Wong.

Use of MuSIS™ hyperspectral (HS) camera system as a non-invasive examination technique to investigate original materials and painting technique. Photo: Francesca Piqué.

Wall painting stratigraphy. Composite image illustrating the stratigraphy of the paintings in Cave 85. The paintings were executed as fine line drawings in red and black ink on a ground preparation covering two base layers of earthen plaster, and then filled in with mineral pigments and washes of organic colorants. Credit: Lori Wong.

Environmental Investigation
 

The environmental monitoring equipment in the cave. Photo: Francesca Piqué.

Environmental data shows a correlation between a loss of painted plaster in Cave 85 with rainfall and corresponding increases in exterior and interior relative humidity (RH) values. RH values inside the cave reached to over 75% the RHequilibrium for NaCl. Given the high values of NaCl found in the plaster the change in RH most likely contributed to the loss of the wall painting. Credit: Shin Maekawa.

Conservation Interventions
 

Conservators at work in Cave 85. Photo: Stephen Rickerby and Lisa Shekede.

Emergency treatment of the paintings included micro-grouting and relaying of areas of exfoliation. Photo: Neville Agnew.

Adhesive testing on simulated panels. To test the long term stability of adhesives and their resistance to salts a series of painted earthen disks were prepared with earth, sand and straw and contaminated with 2% NaCl (wet weight); half of the disk was painted with a chalk and talc ground and malachite paint layer. 3% PVAC was sprayed on half of the disk (to cover part of the painted area and part of the unpainted earthen plaster). The disks were then subjected to repeat wet and dry cycling; the resulting flaking was then treated with a range of adhesives in varying percentages and cycled again. Photo: Lori Wong.

Fixing and consolidation of paint flakes was carried out throughout the cave using a 1% gelatin solution. Photo: Po-ming Lin.

Preparation of the grout which contains clay glass microspheres (Scotchlite K1™), pumice, and small quantities of whipped egg white. Photo: Francesca Piqué.

Lab testing of different grout mixtures. After the appropriate grout component ingredients were identified over eighty grout mixtures were tested for desired performance characteristics and working properties. Photo: Francesca Piqué.

Test earthen plaster panels were grouted in-situ to develop appropriate methods of application. The in situ testing was essential to properly evaluate grout adhesion and salt resistance performance. Photo: Francesca Piqué.

Conservation team preparing for grouting. Photo: Stephen Rickerby and Lisa Shekede.

Grouting of the wall paintings on the west slope. Photo: Lori Wong.

Securing the press after grouting. After grouting, absorbent materials are applied to the surface of the painting and held in place with a press. The absorbent layers absorb salts mobilized by the water in the grout. The painting is monitored and the presses changed regularly over the course of the drying of the grout. Not until the grout has completely dried are the presses removed. Photo: Francesca Piqué.

The Preservation Pencil®, an ultrasonic humidifier, being used to reduce surface and subsurface salts in areas of high salt concentration. Photo: Stephen Rickerby and Lisa Shekede.

Plaster edging repairs to secure fragile areas of painting. Photo: Francesca Piqué.

Training of Dunhuang Academy staff. Photo: Richard Ross.

Dissemination
 

Participants at the Conservation of Ancient Sites on the Silk Road: Second International Conference on the Conservation of Grotto Sites at the Mogao Grottoes, 28 June–3 July 2004. Photo: Dunhuang Academy.

Cover of Conservation of Ancient Sites on the Silk Road: An International Conference on the Conservation of Grotto Sites, Mogao Grottoes, October 1993. Credit: The Getty Conservation Institute.

The proceedings are available in PDF format.