An anonymous reader quotes a report from NPR: Using specialized X-ray imaging, a team of researchers in Australia has revealed a striking painting of a woman’s face hidden under French Impressionist Edgar Degas’ Portrait of a Woman. The researchers believe the auburn-haired woman in the hidden work — which they also attribute to Degas — is Emma Dobigny, who was reportedly one of Degas’ favorite subjects and modeled for him in 1869 and 1870. “Degas painted directly on the underlying portrait with no intermediate ground paint layer using exceptionally thin paint layers, thus little pigment is present to provide hiding power,” the researchers explained in the journal Nature. “The hiding power of paint layers often decreases as oil paintings age.” Even as the traces of a ghostly form emerged over the course of decades, conventional imaging technology could only provide hints of what the hidden portrait looked like. Now, an enhanced process known as X-ray fluorescence elemental mapping gives a far better picture. The technique allowed the researchers to scan for the individual elements — such as iron, zinc and copper — found in different colors of paint. The team said the maps “can be used to deduce pigment use based on the elements observed within the context of the painting.” For example, “Fe and Mn are co-located in the hidden sitter’s hair […] strongly suggesting the use of the brown pigment umber.” The researchers detected cobalt in the face, and deduced that it is “probably present as a blue pigment, which is useful in defining flesh tones.” This chart shows maps of elements the researchers tested in an effort to create a representation of the hidden work.
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