The chemistry of art: teens don goggles and get schooled in the chemical processes behind the ancient art of metalworking.

High school students in Philadelphia are getting an unusual art lesson-from a chemist. To some people, art and chemistry may seem like oil and water: They don't mix. But that's not the case at all, says chemist Tami Lasseter Clare.

Artists work with materials like paint, clay, and metal. Scientists study these same materials to improve them. "Scientific innovations provide artists with new and better materials. And to use these materials correctly, artists need to understand the science behind them," says Clare. "I see science and art as being two sides of the same coin, not as distinct fields of study."

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That way of thinking is a job requirement for someone in Clare's position. As a conservation scientist at the Philadelphia Museum of Art, Clare studies the latest advances in materials chemistry. She hopes to develop a nearly invisible, microscopic coating that will have the ability to keep metallic pieces of art, like Auguste Rodin's bronze sculpture, The Thinker, from getting destroyed by the elements.

In an effort to show others that art and science go hand in hand, Clare teaches workshops on the chemistry of metalworking to high school students.

METAL MAKEOVER

Last fall, Helena Likaj, a sophomore at Nazareth Academy in Philadelphia, and her chemistry classmates participated in Clare's workshop. The students tried their hand at giving grimy metal pieces a chemical face-lift.

When silver is exposed to sulfur-containing substances in the air, the silver undergoes a chemical reaction, or chemical change. The result is a film of tarnish, a dark coating of silver sulfide.

Typical silver polishes can rub away this black layer, but they also remove some of the valuable metal. This could destroy artwork. "For museum pieces, we don't want to lose any of that silver because there may be only a thin coat to begin with," says Clare.

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Helena and her classmates learned a less destructive way to make tarnished silver bright again. They even did an experiment to reverse the chemical reaction that caused silverware to tarnish. They placed the silverware into a tub of boiling water and added baking soda and aluminum foil to the mix. The aluminum combined with the silver sulfide tarnish to form aluminum sulfide. In other words, the tarnish was "transferred" from the silverware to the aluminum foil. This restored the silver to look like new. But more important, the process didn't strip away the original silver; there was no loss of the precious metal.

CHEMICAL CDNNECTIDN

Before Helena and her classmates headed back to school, Clare ended the workshop by explaining how artwork and chemistry have always been intertwined. For instance, in the 16th century, during the cultural movement in Europe known as the Renaissance, artists began using a technique in which a silver compound, such as silver nitrate, would chemically react with other metals in some artwork. The result was a layer of elemental silver deposited onto the art. While this method was state of the art in its day, it became outdated in the mid-1800s, when scientists discovered a process called electroplating that uses electricity to protect and decorate metals with a thin coating of another metal (see Nuts & Bolts, at right.)

Clare is working to develop new advanced clear coatings that could protect famous metal statues, such as those atop Philadelphia's City Hall, from the elements. Recently, she says, chemists concocted new types of resins, a group of clear substances that don't dissolve in

water, that protect art better. The new resins are more protective and also are more environmentally friendly than earlier resins.

Whether Clare succeeds in her goal remains to be seen.

But one thing is certain: She has accomplished her other mission of showing students how chemistry and art are intrinsically linked. "It was very surprising to me that chemistry has a role in producing beautiful artwork. Never would that have crossed my mind before this workshop," says Helena.

AFTER

Auguste Rodin, The Thinker, Philadelphia Museum of Art, after 1992 conservation by a team of museum conservator led by Andrew Lins.

BEFORE

Blue-green areas on The Thinker show the corrosion of the bronze sculpture from pollutants after its having been displayed in an outdoor urban environment for more than 60 years

nuts&bolts

Many artists use electroplating to coat their pieces with a metal. First the art gets put into a tub of liquid that contains a charged form of the metallic coating. Then, the artist connects the art to the negative terminal of a battery. This gives the art a negative charge. The metal ions have a positive charge, so they are attracted to the negatively charged art. A piece of the metal to coat the art is attached to the positive terminal of the battery, resulting in a layer of metal that covers the artwork. The metal coating is both decorative and protective.

webextra For more information about the conservation of The Thinker, visit: www.philamuseum.org /collections/22.398.95-219. html?page=1