Alberti, R., Frizzi, T., Gironda, M., Occhipinti, M., Parsani, T., Seccaroni, C., Tatì, A.
Journal of Cultural Heritage, V58, 2022
The use of Macro-XRF (MA-XRF, an alternative and community-accepted name for large-area micro-XRF scanning) for the compositional analysis of art objects and paintings is well-established, with the technique often being used for the crucial step of pigment characterization that forms the backbone of modern restorative work and practice. Another application of the technique is to help researchers discover how a painting was constructed, to extend the understanding of the history behind the art object, and to learn more about omitted or changed features.
In this scientific art investigation, the Bruker CRONO was used to spatially map Raphael's "Baglioni Entombment", which is permanently on display at Rome's Galleria Borghese.
Special attention was paid to the strontium-based impurities found in the evenly-distributed base gypsum layer. Any additional paint layers on top of the strontium-containing gypsum layer were found to cause a shielding effect - observed as attenuation of the strontium signal. The result is that each measurement pixel had a stronger or weaker strontium signal depending on the layers of paint above it.
By mapping changes in the strontium signal in 2D across the painting researchers were able to extend their understanding of how the painting was constructed. In particular, in findings detailed in a paper recently published in the Journal of Cultural Heritage, the distribution of strontium indicated a phase of restoration to preparation layers, using a different source of gypsum, prior to Raphael commencing the painting itself. The maps also reveal relative the timing of Raphael's abandonment of a female figure from the scene, which had been previously revealed in transmission X-ray images.