Walters Art Museum

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ScienceShot: Atomic Science Keeps Silver Shining Bright

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 only about 20 years—a 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 technique common in the semiconductor industry 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.

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*Correction, 25 March, 12:40 p.m.: Protective coatings now in use last only about 20 years, not less than 10 years, as originally stated. Also, this item clarifies that atomic layer deposition is a technique common in the semiconductor industry.