Dunhuang Murals

Mogao was first cut in 366 CE, into the cliff at the eastern foot of the Mingsha dunes at Dunhuang. Caves were opened over a thousand years, from the Sixteen Kingdoms to the Yuan, leaving more than seven hundred along some sixteen hundred metres of cliff, of which over four hundred and ninety still hold murals and sculpture.

In 1944 the National Dunhuang Art Research Institute was founded, the first time the caves had full-time staff; it became the Dunhuang Cultural Relics Research Institute in 1950 and was expanded into the Dunhuang Academy in 1984. In 1961 Mogao was designated a national key cultural relic protection site; in 1987 UNESCO inscribed it on the World Heritage List, among China's first World Heritage sites.

Mogao is a Buddhist complex in which architecture, painted sculpture and mural form a single whole: the cave group runs more than sixteen hundred metres and divides into southern and northern zones, with over 45,000 square metres of mural and more than three thousand painted sculptures, the largest of them 35.5 metres tall and the largest single mural about 47 square metres.

The Dunhuang cliff is loose conglomerate and cannot be painted on directly. The painters first spread a mud layer, then a coat of white lime, and only then was the surface smooth enough: the painting sits on this prepared ground.

The pigments were mostly natural minerals: cinnabar and vermilion for red, lapis lazuli for blue, verdigris for green, gypsum and talc for white, mica for a touch of brightness. These minerals are stable and opaque, and although the range of colours was narrow, mixing and layering produced every variation — which is why the colours of Mogao can still be read after a thousand years.

From the late 1970s into the early 1980s, researchers sampled and analysed pigments from more than forty caves, identifying over twenty inorganic mineral pigments and establishing that light is one of the main causes of colour change in wall painting. Today the Dunhuang Academy has digitally recorded the murals of two hundred and ninety caves and built panoramic walk-throughs of more than a hundred and sixty: when the door is shut, these walls exist a second time in data.

The murals are the largest holding at Mogao and the hardest to keep: salt efflorescence, flaking paint and detachment of the plaster are conditions somebody has been watching and treating all along. From joint conservation with institutions at home and abroad to scanning the walls sheet by sheet into data, the Academy has really been doing one thing — keeping the colours on the wall, and keeping a copy of them somewhere else as well.

Visitors go in with a guide, one cave opened at a time, and the door is locked behind them. For most of sixteen hundred years these paintings have waited in the dark in exactly this way, for the next door to open.