Neutron Activation Autoradiography of Oil Paintings

A very moderate, non-destructive radioactivation of oil paintings, induced by thermal neutron bombardment, such that approximately only one in 1012 of the atoms comprising any painting is transformed into a radioactive species, has been found to produce temporary radioactivity sufficient to expose photographic film placed in direct contact with the paintings. The resulting autoradiographs resemble conventional X-radiographs in that they reveal structural details in depth of both the painting and its support. Since the radioactivities arising from the different elements within a painting decay in different manners and at different rates, a series of significantly distinct auto radiographs can be obtained of any painting by making exposures through appropriate filters and at varying times following the original activation. Analysis of such a series of autoradiographs permits the identification of a number of the pigments used in a painting, together with information about the manner in which they were origi...