Physicists paint a clearer picture

Physics World
July 1998, page 10

Scientists and artists have traditionally viewed one another with deep suspicion. But as Sharon Ann Holgate reports, physicists can make an impact in the world of art conservation    

Physics is probably the last thing on our minds when we’re admiring a beautiful painting, but it plays a large part in determining if our great-grandchildren can enjoy the same experience. Art conservationists have for some time been using various physics-based techniques to help them in their work. Raman spectroscopy, scanning electron microscopy and X-ray diffraction can help them to identify the pigments in a painting. Meanwhile, lasers are being used to show cracks in the surfaces of sculptures, and could help to clean statues and paintings.

The latest technique to cross over from the world of physics is electronic speckle pattern interferometry. When used with a tensile tester, this method can shed light on how paintings decay. “We want to understand how cracks develop,” says Christina Young, a physicist who divides her time between the conservation department at London’s Tate Gallery and the mechanical engineering department at Imperial College, London. She is using the technique to predict the onset of cracking in paintings, so that the problem can be minimized by altering the environmental conditions in which the paintings are stored. Young is co-ordinating the project, which for the first time brings together scientists and conservationists from the Tate, Imperial, the UK’s National Gallery and the Courtauld Institute.

Trying to work out the best storage and hanging conditions is a complicated problem, as paintings are surprisingly complex systems. Canvases are usually covered by a layer of glue, also known as the “size layer”, which is in turn covered by a primer, usually a neutral-coloured paint. Various layers of paint are then built up on top of the primer. Light and pollution can cause the paint to fade, and cracking results from changes in temperature and humidity.