Vincent van Gogh Recycled

A new method of Synchrotron radiation based X-ray fluorescence elemental mapping has allowed the revealing and reconstruction of a portrait underneath a portrait, it has also allowed us to gain more insight into the genius that was Vincent van Gogh. Previous techniques of conventional X-ray radiation transmission radiography (XRR) and infrared inflectography (IRR) helped to initially recognize a faint head under the surface painting of van Gogh’s Patch of Grass. However, due to the limitations of these methods, the revealed face could not be identified and the new method of Synchrotron radiation based XRF was implemented. XRF works based on the principle of the photoelectric effect: a core level electron is promoted out of the atom. The painting was subjected to an X-ray bundle from a synchrotron radiation source, and the fluorescence of the layers of paint was measured. This technique is advantageous because the measured fluorescence is unique to each element as the intensity of the fluorescence is proportional to the number of excited atoms. This allows each atom in the paint pigments to be identified and charted. Additionally, the high-energy fluorescence of the smaller elements will not be masked by that of the larger elements. X-ray absorption near edge structure (XANES) was performed to determine which molecule the antimony was part of and therefore which pigment was used for the underlying portrait of the unknown face. XANES spectra are dependent on the multiple scattering resonances of the excited photoelectron at the atomic absorption site. The K-edge spectra from the XANES was compared to that for Naples yellow (Pb₂Sb₂O₇) and antimony white, (Sb₂O₃) both which contain antimony in the molecular formula for the pigment. An analysis with μ-XANES at the Sb L_III and L_I edges indicate a spectrum of Naples yellow. Another series of XRF analyses were conducted on heads in paintings by van Gogh, which verified the presence of Hg, Zn, Pb, and Sb. Elemental distribution maps were constructed to give approximations to the colors van Gogh used.

It is estimated that about 1/3 of van Gogh's paintings are paintings underneath a painting.