Combining Art and Science

This is a confession. I love cells. However, if this were an essay for my German teacher at secondary school she would, given the name of this blog, award me a “Themenverfehlung” (basically completely missing the point of the essay question), which she did on a semi-regular basis. I could argue that in the broadest sense this post is also about cells, because cells were necessary for the creation of this work of art as well as for the analysis. But I admit that’s a bit of a stretch.

Anyway. I found this new paper published in Scientific Reports (Thurrowgood et al, 2016), which is simply entitled, ‘A Hidden Portrait by Edgar Degas’. The Australian research group, comprised of art curators and X-ray technology specialists, used a technique called X-ray fluorescence to study “Portrait of a Woman”, which hangs in the National Gallery of Victoria, Australia. Normal X-ray analysis had already revealed that an earlier portrait of a different woman lies underneath what is currently visible:

figure 1

Visible image of “Portrait of a Woman” (left) and conventional X-ray imaging (right) – copied from Figure 1

Conventional X-ray technology relies on the different densities of the materials/pigments in the painting. The denser areas absorb more of the X-rays and the X-ray film behind is less exposed than behind less dense areas, just like in a chest X-ray, for example. However, X-ray fluorescence is a more sensitive technique because it can detect specific elements in the painting. When atoms are hit by high energy X-rays some of the electrons close to the atomic nucleus (the “inner shells”) can be flung out of the atom entirely. This leaves a hole for electrons to fill and when these electrons “fall” into the inner shells energy is released in the form of electromagnetic waves, which are characteristic for different atoms:

XRF_Theory_Schematic

Schematic of X-ray fluorescence – copied from this link

This technique is not entirely new, but as far as I understand this was the first time it has been used for a large-scale analysis of a painting. Using the physical properties of different atoms, Thurrowgood et al. created so-called elemental maps to determine which parts of the hidden portrait contained which elements.

figure 3

Elemental maps – copied from Figure 3

By analysing which elements are found in the same areas the researchers could trace back which pigments were used and therefore make educated guesses about the original colour of the painting. For example, the hair contained a lot of iron and manganese, which are often found together in the brown umber pigment.

figure 6

False colour image reconstruction of the hidden portrait of Mlle. Dobigny – copied from Figure 6

Mademoiselle Dobigny was one of Degas’ favourite models, but who knows why he kept her portrait for so long before deciding to paint over it. The reasons are certainly less obvious than in Georges Seurat’s painting “Young Woman Powdering Herself” (Courtauld Institute of Art, London): he concealed the only known self-portrait of his behind a mirror, watching the young woman who also happened to be his lover…

Reference and further reading:

Thurrowgood D, Paterson D, de Jonge MD, Kirkham R, Thurrowgood S, Howard DL (2016) A Hidden Portrait by Edgar Degas. Scientific Reports 6: 29594

New York Times article on Degas’ painting

Courtauld Institute of Art blog on Seurat’s painting

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