Ultraviolet vs Infrared: The Vienna Art Heist, 1994

In 1994, inside Vienna’s Kunsthistorisches Museum, detectives inspected a stolen Rembrandt with a flashlight set to 365 nanometers, lighting up a dozen glowing streaks across the canvas. Ultraviolet-shorter than visible light-makes certain materials fluoresce, showing repairs and hidden fingerprints. But when the same painting faced 900-nanometer infrared, a faint outline appeared beneath the surface, revealing changes Rembrandt made decades earlier. Ultraviolet exposes surface-level secrets-fingerprints, fresh paint, even faded ink-while infrared sees deeper, penetrating the layers to find drawings, watermarks, or hidden signatures. In this art heist, ultraviolet caught the forger’s fingerprints, but only infrared exposed the painting’s true past. To keep the two straight-ultraviolet finds what’s on top, infrared finds what’s underneath. Both turned out vital, but forensics hinged on knowing the difference.