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New anti-tarnish coating to be tested at Walters


BALTIMORE, MARYLAND Polishing the silver may no longer be a common
household chore, but it’s still a tedious part of the to-do list at
many art museums. Armed with Q-tips, chemical coatings, and lots of
elbow grease, art conservators do constant battle with tarnish, a
thin layer of sulfide that forms on silver when it’s exposed to air.
Constant polishing can wear down artifacts, however, and the
protective coatings now in use cover the objects unevenly and last
less than 10 yearsa short time for museums charged with preserving
centuries-old objects for future generations. Now, a group of
materials scientists thinks that it’s hit upon a solution. Using a
commercial technique called atomic layer deposition (ALD), they
coated pieces of silver with layers of aluminum oxide only 1 atom
thick. By gradually building up the number of layers, the researchers
could precisely control the thickness of the film in the silver’s
every nook and cranny. One application of an ALD coating could
protect a silver artifact for more than 80 years, the team reported
this week at the March meeting of the American Physical Society. With
the help of the Walters Art Museum in Baltimore, the researchers will
soon test the process on their first work of art by applying the ALD
film to strips of silver (inset) from the late 15th century Spanish
cross pictured above. They expect the coating to be invisible and
longer lasting than standard methods, but art lovers have little to
worry about if they’re wrong: The process is completely reversible.

Elliot Nesterman