“Kan kun være malet af en gal Mand!” (“Can only have been painted by a madman!”) appears on Norwegian artist Edvard Munch’s most famous painting The Scream. Infrared images at Norway’s National Museum in Oslo recently confirmed that Munch himself wrote this note.

The inscription has always been visible to the naked eye, but the infrared images helped to more clearly distinguish the writing from its background. Comparing it with the artist’s handwriting then clearly proved Munch’s authorship.

“The finding closes the question about who the author of the inscription was,” says Mai Britt Guleng, a curator at the National Museum. “The [infrared] photo gave a clear image of the sentence, and this made it possible to systematically compare the handwriting, which is identical to Munch’s. The size of the letters are also too small for anyone to have written them as an act of vandalism.” —Scientific American