Scientists at the Louvre have discovered the secret to the Mona Lisa’s face

THE Mona Lisa’s lure is so strong that Louvre Museum officials find it wise to keep her safely stowed behind bulletproof glass. She is let out of her protective cage once a year, for a whiff of fresh air. And this is when many a researcher would love to get their hands on Leonardo da Vinci’s most famous muse, in order to find out more about how she was painted.

For a long time, scientists and curators have wondered how da Vinci created shadows on her face with seemingly no brushstrokes or contours. Art experts call this shadowing technique sfumato—like the Italian word for smoke, fumo. Experts have long suspected sfumato shadowing has something to do with the glazes that da Vinci used above the paint layer. But proving this has been difficult because snatching a sample of the Mona Lisa’s face for chemical analysis is, unsurprisingly, frowned upon. …