What material is the protective case of the Mona Lisa made of?

The protective case of the Mona Lisa is made of bulletproof glass.

The case does more than stop physical attacks. Since 2005, the Louvre has displayed Leonardo da Vinci’s portrait inside a specially designed enclosure that controls temperature and humidity. Those conditions help protect the painting’s fragile poplar-wood panel, which has warped over time and developed a crack.

The glass has also protected the painting during several notorious incidents. In 1956, a visitor threw a stone that damaged the paint near the sitter’s left elbow; later attacks, including a 2009 ceramic cup and a 2022 cake-throwing incident, struck the enclosure rather than the artwork. During the painting’s 1962–1963 American tour, the protective case even shielded it from water when a faulty sprinkler nearly drenched the display.

A common mix-up is confusing the case with the painting’s support: the Mona Lisa itself is painted in oil on a poplar panel, not on glass.