Hidden Van Gogh Revealed

It is well-known that Vincent van Gogh often painted over his older works. Experts estimate that about one third of his early paintings conceal other

The analysis of the painting ‘Patch of Grass’ by Vincent Van Gogh by means of an advanced form of non-destructive X-ray analysis revealed in unprecedented detail the original portrait, also by Van Gogh, over which the landscape was painted. Courtesy of DESY Hamburg

compositions beneath them. A new non-destructive technique, based on synchrotron radiation induced X-ray fluorescence spectroscopy, allows this type of hidden painting to be revealed. An international research team successfully applied the technique for the first time to van Gogh’s painting entitled Patch of Grass, revealing in unprecedented detail a portrait of a woman behind the newer work of art.

Since techniques, such as conventional X-ray radiography, that have traditionally been used to reveal concealed layers of paintings have limitations, the team, which includes members from Delft University of Technology in The Netherlands and the University of Antwerp in Belgium, took a different approach. Together with experts from the Deutsches Elektronen-Synchrotron in Hamburg and the Kröller-Müller Museum, TU Delft materials expert and art historian Dr Joris Dik, and University of Antwerp chemistry professor Koen Janssens subjected the painting to an X-ray bundle from a synchrotron radiation source, and the fluorescence of the layers of paint was measured.

The new technique has the major advantage that the measured fluorescence is specific to each chemical element. Therefore, each type of atom (e.g. lead or mercury) and also individual paint pigments can be charted separately. The benefit of using synchrotron radiation is that the upper layers of paint distort the measurements to a lesser degree. Moreover, the speed of measurement is high, which allows relatively large areas to be visualized.

The experimental set-up

Patch of Grass was painted by Van Gogh in Paris in 1887 and is owned by the Kröller-Müller Museum. Previous research had already discovered the vague outline of a head behind the painting. It was scanned at the synchrotron radiation source DORIS at Deutsches Elektronen-Synchrotron DESY in Hamburg using an intense but very small X-ray bundle. Over the course of two days, the area covering the image of a woman’s head was scanned, measuring 17.5 x 17.5 cm.

The measurements enabled researchers to reconstruct the concealed original painting in unparalleled detail. In particular, the combination of the distribution of the elements mercury and antimony (from specific paint pigments) provided a ‘color photo’ of the portrait underneath. The reconstruction enables art historians to better understand the evolution of Van Gogh’s work, and the applied technique is expected to pave the way for research into many other over-painted works of art.

View a film explaining the research

View a film of the work in progress

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