Sponges filled with iron nanoparticles make lifting dirt easy
When a priceless work of art becomes dirty, running it through the dishwasher obviously isn't an option. But even the most sensitive of modern cleaning techniques come with problems - which one researcher says he can solve with a gel sponge and a magnet.
Many current conservation techniques use specially designed gels that can be placed on isolated dirty spots of a painting. In this way, specific cleaners can be applied to a small area of an artwork without the cleansing gel running or removing the paint along with the dirt.
But getting the sticky gel off at the end can be tricky. Residue of gel and cleaner can remain both on and under the surface being cleaned, marring the art. And using any kind of abrasive removal technique on a delicate painting comes with its own problems.
Piero Baglioni, a chemist at the University of Florence, Italy, says he has found a way around these problems - by creating a gel that can be removed with a magnet.
"It will replace the old method because it's easier," Baglioni says.
Baglioni and his colleagues detail their production of a gel sponge containing magnetic nanoparticles in the latest issue of the journal Langmuir1.
Sponge bath
Baglioni's gel consists mainly of a polymer (polyethylene glycol and acrylamide) impregnated with iron nanoparticles. This gel is firm enough to be cut with scissors into 'sponges' of specific shapes required for cleaning. Such sponges can be loaded with a wide array of cleaning materials, as required for oil paintings or marble sculptures for example, and applied to the parts of the artwork that need cleaning.
Once applied, the cleanser leaches onto the top surface of the artwork, where it should dissolve the dirt to be removed. As the upper surface of the gel dries during the cleaning process, an osmotic pressure gradient is set up within the gel that then pulls the cleaning solution back into the sponge and away from the surface of the painting or sculpture. This trick works thanks to the fact that the gel is generally more inclined to soak up water-based substances than the surfaces being treated.
Simply placing a magnet above the piece of gel then removes it from the painting's surface without damaging the art.
"To the best of our knowledge, the ... responsive chemical gel represents one of the most advanced, versatile systems for cleaning works of art, avoiding any side effects," the researchers write in their paper.
Aviva Burnstock, head of the Department of Conservation & Technology at London's Courtauld Institute of Art, notes the importance of being able to remove the sponge as well as the cleaning material that the sponge was impregnated with.
What's interesting about Baglioni's system, she says, is how his sponge can be used to treat such small areas; other gels are not necessarily so good at limiting how much of the painting is exposed to the cleaner. "It's not a bad idea," she says. "It could be useful for very delicate surfaces."
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