Covered paint layers in Old Masters revealed

In a mock-up of a Rembrandt painting, buried paint layers from a portrait on a reused panel that is overpainted by a second portrait have been uncovered by scanning macro-X-ray fluorescence (MA-XRF). The original painting, entitled "An Old Man in Military Costume" had previously been examined by X-ray radiography, neutron activation autoradiography and IR reflectography, all of which revealed a partial or blurred impression of a facial image beneath the main portrait.

Now, scientists have prepared a full-scale mock-up of the painting, including both the lower and upper portraits, being as accurate as they could to reproduce the primer, imprimatura, paint stratigraphy and pigment compositions. It was examined by three MA-XRF scanners to see if a detailed image of the lower portrait could be obtained and whether it would be worthwhile transporting the original painting from the J. Paul Getty Museum in Los Angeles to a nearby synchrotron facility for MA-XRF examination. The results are described in Journal of Analytical Atomic Spectrometry.

Scans of the entire painting, the facial area, and more detailed scans were taken. Based on the element distributions of calcium, iron, mercury and lead and their figures of merit, the research team predicted that it would be possible to acquire a sharper visualisation of the hidden portrait in the original painting using the two synchrotron-type instruments. In contrast, the mobile tube-based instrument failed to resolve the complete face of the hidden portrait.

So, it would be worth the effort of transporting the original painting for closer examination by this non-destructive technique. While the team pointed out that reworking of the original face might prevent it from being fully resolved, it would still help experts to compare the hidden painting with Rembrandt's body of work.