The Mogao Grottoes, a collection of more than 500 ancient Buddhist temples carved into the cliffs near Dunhuang in north-western China, were a key stop for the intrepid travellers who exchanged goods and information on the Silk Road—the ancient equivalent of the information superhighway. Dunhuang was one of the first trading cities in China encountered by Western merchants, and the final supply stop for those making the long push westward, so travellers visited the richly decorated temples (dating from the fourth to the 14th centuries) to pay their respects. Fast-forward more than 500 years and the Unesco World Heritage Site remains a popular tourist destination.
The caves face a number of preservation challenges, so for the past 27 years, the Los Angeles-based Getty Conservation Institute (GCI) has been working with the Chinese government and the Dunhuang Academy to ensure that the grottoes and their decorative interiors survive. This work is the basis for the Getty Center’s exhibition Cave Temples of Dunhuang: Buddhist Art on China’s Silk Road (until 4 September), which brings a piece of the Silk Road to Los Angeles in the form of artefacts, life-sized cave replicas and cutting-edge technology.
Taming the elements
Neville Agnew, a senior project specialist at the GCI, says that controlling the influx of wind-blown sand from nearby dunes was one of the first issues addressed when the project began in 1989. “Thousands of cubic metres of sand had to be removed by hand each year,” he says. The movement of sand over the cliff had worn away the rock to such an extent that some of the caves’ roofs had thinned and collapsed. The solution was surprisingly simple: erect a 6ft-high, three-mile-long fence made from a synthetic knitted fabric, at a cost of around $15,000, and create a natural barrier by planting desert-adapted local species of plants and shrubs. Agnew says that these measures have reduced the sand problem by 60%.
Cave 96—a nine-storey temple housing a colossal Tang dynasty Buddha. © Dunhuang Academy
Guided by the GCI’s “whole-body medicine” approach to site preservation, in which elements are looked at together and not in isolation, the early years of the project focused on assessing the site, which included monitoring the weather and temperature levels, examining the rock’s geological stability (the site is in an earthquake zone) and identifying pigments and the extent to which they had changed over time. They also ran training programmes for local people.
Finding the source of moisture or water vapour in the caves was difficult because it comes from several places. The salt in the rock absorbs this moisture and liquefies; when it dries out, it crystallises. This repeated act of liquefaction and crystallisation harms the wall paintings. Agnew says that, although visitors “may raise the cave’s humidity levels by 5% over the ambient [levels]”, the repeated act of opening and closing the doors when humidity levels are high is the more pressing concern, because it “allows for a rapid exchange of air” inside and outside.
Protecting Big Buddha Cave
Around one million tourists visit the 60 or so caves that are open to the public each year. Although different caves are accessible from year to year, there are four on everyone’s “must-see” list, including the Big Buddha Cave—a nine-storey structure built in the seventh century to house a 35.5m-high Tang dynasty Buddha. A visitor management plan, developed to determine how many people could visit the cave without having a negative impact on it, found that the ideal number is 6,000 people, spread evenly throughout the day. A visitors’ centre was built ten miles from the site to help to control the flow of tourists.
Cave 85 was used as a ten-year case study to determine how to conserve the site’s wall paintings. The late Tang dynasty cave (AD848-907) suffers from the same issues as others in the complex. The painted mud plaster’s detachment from the rock “continues to be the single greatest threat to the wall paintings”, Agnew says. This separation probably occurred soon after the caves were finished, but “was exacerbated by the build-up of salts”. Ceiling decorations are particularly vulnerable, especially in this earthquake-prone area. The team studied salt extraction, analysed the pigments and binders and researched which materials were best for re-laying the lifting paint. They also developed a technique to adhere the wall paintings to the underlying rock and experimented with a new display that encouraged visitors to view the paintings, lit by LED lights, from a raised platform.
Three of the eight cave replicas commissioned by the academy are in the Getty’s exhibition. They were hand-painted by a team of artists who “described [working on them] as almost a spiritual exercise”, Agnew says. Visitors to the exhibition can also experience the caves in 3D, with the aid of stereoscopic immersive technology, and can see around 40 of the 50,000 manuscripts, silk paintings and sketches from the Library Cave. Among the key pieces from this cave is the frontispiece of the Diamond Sutra (AD868)—a sacred Buddhist text that is said to be the earliest completed book. The piece has been lent by the British Library in London.
Agnew hopes that visitors will experience the same awe felt by people hundreds of years ago. “It must have had an immense impact on travellers coming out of the desert. They probably thought they were in paradise,” he says. “It’s akin to Medieval peasants visiting the cathedrals in Europe and being struck dumb by their wealth, beauty and grandeur.”