Reversible gel restores artwork

In an advance that could help conservationists restore paintings to their original glory, chemists have developed a cleaning product that switches from a free-flowing liquid to a viscous gel.

The researchers tested the material on a 14th-century painting from the National Gallery in Siena, Italy. Layers of resin applied after the painting’s completion had, over the centuries, dulled the artwork’s color. The gel brightened the test spot on the painting, and analyses of the gel after its use showed that none of the pigments had been removed from the original paint layer. The researchers describe their product in the Sept. 28 Langmuir.

The so-called rheoreversible gel consists of a cleaning solvent mixed with a polymer called polyallylamine. Initially, the polymer was in a liquid form. However, when researchers bubbled carbon dioxide through it, the polymer chains linked up.

In this viscous state, the gel can be applied to a localized spot on a painting’s surface where the cleaning solvent can do its work. Adding a bit of diluted vinegar causes the gel to revert to a liquid that can be gently wiped away with a cotton swab.

Because other cleaning gels for artworks can’t switch states like this, they are difficult to remove without disturbing the paint, particularly when they seep into the artwork’s cracks and pores, says organic chemist Richard Weiss at Georgetown University in Washington, D.C.

Weiss developed the gel with his colleagues at the University of Florence in Italy.