Answer: Isotope Analysis

As long as humans have been producing art (and placing value on who created it and how rare it is), forgers have been painstakingly recreating that art to pass off as the authentic creations of the original artist.

Historically, forgeries were detected by careful comparison of the actual techniques (brush strokes, signatures, etc.), unusual marks on the frame or canvas, and chemical analysis of paint that contains pigments not available at the time the artist was working.

The newest tool used by forensics teams is isotope analysis. As a result of worldwide testing of atmospheric nuclear weapons in the 1950s, an abundance of nuclear isotopes cesium-137 and strontium-90–nuclear isotopes not found in nature prior to the advent of the nuclear age–are found in canvases, paint, and other components of artwork created after that time.