sciencehabit writes: 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 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 commercial technique called atomic layer deposition (ALD), they coated pieces of silver with layers of aluminum oxide only 1 atom thick.  One application of an ALD coating could protect a silver artifact for more than 80 years, the team reports.  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.