"After some 40 years of study, the Italian institute of nuclear physics has finally solved the mystery of Peggy Guggenheim’s Léger. The painting’s authenticity was first queried by the art historian Douglas Cooper in the 1970s. The museum curators therefore took the precaution of removing the painting from public exhibition without having any formal proof that Constrastes de formes was actually a forgery.
During the 1950s and 1960s, nuclear tests carried out around the world doubled the radiocarbon present in the atmosphere, leaving indelible traces on all living organisms. By measuring the level of radiocarbon on the canvas, researchers at the institute of nuclear physics concluded that the cotton used to weave the canvas could not have been harvested before 1959, proving the Contrastes de formes could not have been painted in 1913-1914."