In 2008, a researcher in the Netherlands used an advanced X-ray technique to show that Vincent van Gogh's 1887 work "Patch of Grass" was actually done over an earlier painting of a woman's face. The practice is thought to have been common for van Gogh, with an estimated one in three of his earlier paintings overlaying older works. Now, using a similar scanning technique, researchers in Australia are reporting in the journal Scientific Reports that they have uncovered the striking face of a woman that lay hidden beneath Edgar Degas’ "Portrait of a Woman" for 140 years, reports the New York Times. The painting had actually been criticized as long ago as 1922 for its discoloration, reports the Guardian.
Researchers think the face belongs to one of Degas' favorite models, Emma Dobigny, and that it's only possible to see because the paints Degas used over it were so thin. The scanner employs a narrow, brilliant X-ray beam a million times brighter than the sun that's generated by a machine called a synchrotron, which is a type of particle accelerator. The technique forced atoms in the paint to fluoresce and reveal their elemental makeup. Mercury sulphide, for instance, provides the vermillion that colors the model's cheeks and lips, while iron and manganese hint at Degas' use of umber for brown hair. The image is so high-res that it even shows the imprints of the paintbrush bristles within each stroke. One researcher says when he first saw the scan it was "one of the most exciting times in my scientific career." (A computer is helping Rembrandt paint again.)