Speaker
Dr
Thomas Calligaro
(Centre de recherche et de restauration des musées de France C2RMF)
Description
Beams of X-rays and, to a lesser extent, ions and neutrons (with the neutron autoradiography technique) have been successfully applied to collect elemental maps of historical paintings. Such probes can notably reveal the pigment distribution within entire paintworks through their elemental fingerprints without contact and in a non-destructive way. The comparison of the recorded images with pictures taken with routine imaging techniques (e.g. visible, UV, IR photography and X-ray radiography) provide curators, art historians and restorers information concerning the painter techniques and choices, and can help in the preparation and the monitoring of restorations.
The presentation focus on two elemental imaging techniques developed at the C2RMF. The first relies on the use of a scanning sub-millimetre X-ray beam of a transportable, versatile and cost-effective XRF scanner designed and built at the C2RMF. Initially developed at the synchrotron, such technique has been transposed to the laboratory under the name MA-XRF [1]. The second approach is based upon a scanning external milli-beam of protons of a few MeV in PIXE mode at the AGLAE accelerator facility [2]. The merits and limitations of both methods will be discussed. For example excitation protons confers to PIXE a probing depth that vary with incident energy, an improved yield for light elements compared to heavier ones, and a easy beam scanning. On the other hand, a scanning X-ray beam is probing deeper, exhibits unique features such as Compton scattering and is less susceptible to induce modifications in paint materials than ion beams. Finally, the penetration of neutrons and gamma-rays permits to image isotopes independently of the paint layer thickness and stratigraphy.
The capabilities and limitations of MA-XRF and PIXE imaging of will be illustrated with case studies carried on paintworks. The Saint John the Baptist by Leonardo da Vinci (muse du Louvre) was studied using MA-XRF and paintings from the 16th and 19th c. were investigated using both MA-XRF and scanning-PIXE.
[1] E. Ravaud, L. Pichon, E. Laval, V. Gonzalez, M. Eveno, T. Calligaro, Development of a versatile XRF scanner for the elemental imaging of paintworks, Appl. Phys. A122 (2016) 17
[2] T. Calligaro, V. Gonzalez, L. Pichon, PIXE analysis of historical paintings: Is the gain worth the risk?, Nucl. Instr. And Meth. B363 (2015) 135
Primary author
Dr
Thomas Calligaro
(Centre de recherche et de restauration des musées de France C2RMF)
