Published online 22 April 2008 | Nature | doi:10.1038/news.2008.770

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Ancient Buddhas painted in oils

Were painters on the Silk Road way ahead of the Europeans?

Tiny samples scraped from these cave images revealed an ancient artistic trick.National Research Institute for Cultural Properties, Tokyo (Japan).

Artists in Afghanistan used a primitive form of oil paint on cave walls hundreds of years before it became common practice in Europe, according to new research.

Yoko Taniguchi of the National Research Institute for Cultural Properties in Tokyo and her co-workers analysed samples of Buddhist paintings in caves at Bamiyan in Afghanistan, made in the mid-seventh and early eighth centuries AD. They say that the paint layers contain pigments apparently bound within oils, perhaps extracted from walnuts and poppy seeds.

But Jaap Boon, a specialist in the chemical analysis of art at the Institute for Atomic and Molecular Physics in Amsterdam, the Netherlands, cautions that this conclusion must be seen as tentative until more detailed studies have been done.

The Bamiyan caves sit behind the gigantic statues of Buddha that were destroyed by the Taliban in 2001. The paintings, showing robed Buddhas and mythical creatures, were also defaced but not obliterated. The Bamiyan caves are now a designated UNESCO World Heritage site.

The researchers removed tiny samples of the painted surface (typically less than 1 millimetre across) for analysis using state-of-the-art techniques.

A closer look

Taniguchi’s collaborators used X-ray beams produced by the European Synchrotron Radiation Facility in Grenoble, France, to determine the composition and crystal structures of pigment particles in the colours. The synchrotron facility produces extremely bright X-ray beams, which are essential for getting enough data from such small samples.

Meanwhile, spectroscopic methods, which identify molecular structures from the way their vibrations cause light absorption, were used to identify the organic components of the paint layers. The findings are described in a paper in the Journal of Analytical Atomic Spectrometry1.

The researchers found pigments familiar from the ancient world, such as vermilion (red mercury sulphide) and lead white (lead carbonate). These were mixed with a range of binders, including natural resins, gums and possibly animal-skin glue or egg — and oils.

Slow to dry

This is surprising. All pigments need something liquid to bind them together, and primitive painters used a range of organic substances, from egg to animal fat or glue from boiled animal hide, to do that. But oils are slower drying – a handy quality if you’re attempting subtle Renaissance-style blending of colours on the canvas, but generally seen as a disadvantage in earlier times. What’s more, the translucency of many oil paints isn’t obviously what you want for painting on walls.

So it’s questionable whether those properties would have been of much use in this setting, says Boon. “It doesn’t make a lot of sense to use oils.” He says that it would be really difficult to keep the paint in good condition for a long time in an environment such as this, exposed to damp, fungi and bacteria.

The concept of using oil binders for pigment goes back further than is sometimes supposed. It was mentioned in the late fifth century by the Byzantine writer Aëtius, and a recipe for an oil varnish (in which a drying oil is mixed with natural resins) was listed in an eighth-century Italian manuscript. In the twelfth century, a German Benedictine monk called Theophilus describes how to make oil paints for interior decorating — specifically for painting doors. Oil paints are also known from this period on Norwegian churches.

But this sort of oil paint was long thought fit for only rather lowly uses. Not until the fifteenth century did the Flemish painter Jan van Eyck and his brother Hubert refine the technique to create stunningly rich and durable colours.

Don’t touch the walls

Boon says it is possible that the results are just down to contamination — microorganisms on the rock surface, say, or the fingerprints of people touching the paintings (something encouraged in Buddhist tradition). He says that other techniques that really pin down the identity of the organic molecules should be applied before jumping to conclusions.

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But Marine Cotte of the Centre of Research and Restoration of the French Museums in Paris, a co-author of the study, is convinced of the conclusions. She says that oils have an unambiguous spectroscopic signature, and that their molecular components have been confirmed by the technique of chromatography. She adds that the oils are found under other layers of paint, which helps rule out the idea of contamination.

It’s not clear who these artists were, the researchers say. They were probably travelling on the Silk Road between China and the Middle East, and may have been bringing with them specialist knowledge from China.

Cotte says that these studies should aid efforts to preserve the paintings. “It helps you do that if you know what is there,” she explains: knowing if oil or egg was the predominant binder would help in choosing the most appropriate cleaning procedures, for example. 

  • References

    1. Cotte, M. et al., J. Analyt. Atomic Spectrosc. (in press, 2008)
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