Salad Dressing-Like Mix Restores Art

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June 1, 2007 — A salad dressing-like mixture of water, a bit of oil and a sugar-like molecule can safely clean ancient frescoes, according to a new nanotechnology research.

Scientists at the University of Florence, Italy, have discovered that the oil-in-water microemulsion — basically tiny droplets of oil suspended in water — can penetrate a painting’s pores and scrub away grime and acrylic resins.

The potion has proven particularly effective in cleaning frescoes that had been coated in thick layers of paraloid, an acrylic copolymer widely used by conservators in the 1960s. While the paraloid was intended to offer a protective coating for artworks, it turns out the aging of the acrylic, and reactions with calcium salts beneath the coating, produce a disastrous effect decades after the treatment.

"All the colors, especially the background, appear darker and the coated surface is very shiny," chemist Piero Baglioni and colleagues at the University of Florence wrote in the current issue of the American Chemical Society journal, Langmuir.

Previously, organic solvents, traditionally used in restoration, have been ineffective in removing the acrylic copolymer.

"Conventional techniques can remove polymeric material at the surface, but they are almost completely useless in cleaning paraloid from the porous structure of the frescoes. In this case, we found that something like salad dressing can be a great alternative," Baglioni told Discovery News.

The key compound in creating the microemulsions is a sugar-like molecule that makes it possible to mix water and oil — a process that doesn’t occur naturally.

The result is the formation of tiny droplets of oil that are roughly 10 nanometers in size.

"The droplets feature a very high interfacial area between the oil and the water. This very high surface area is the trick we use to extract polymers from the frescoes," Baglioni explained.

Using the microemulsions is rather simple. The researchers protect the painting with thin Japanese paper and pour the microemulsions — in the form of a paste or a gel — onto the wrapped artwork. After 10 minutes to a couple of hours, the paste or gel is removed, and with it, any grime and paraloid.

"It is a cheap, simple and environmentally friendly way to clean masterpieces. Using just one percent of oil, we basically managed to make water a very aggressive cleaning agent," Baglioni said.

Daniela Dini, a restorer in Florence who was not involved in the study but tried Baglioni’s technique, agrees that it is a promising new technology.

"It should not be considered a potion that magically cleanses any masterpiece. However, I must say that it works well in removing paraloid, which unfortunately has been applied to many frescoes," Dini told Discovery News.