Depth profiling reveals multiple paint layers of Louvre Renaissance paintings using non-invasive compact confocal micro-X-ray fluorescence

Abstract

The High Renaissance marks one of the most significant and prolific periods of artistic production in painting. Artists of this epoch advanced many aspects of pictorial art that continue to be debated and researched today. The typical painting technique during this time period consisted of superimposing multiple layers of thinly applied paint to achieve realistic optical impressions and desired visual effects. The presence of multiple thin layers in Renaissance paintings presents a challenging case study. In the work presented here, a laboratory-based confocal micro-X-ray fluorescence analysis (CXRF) spectrometer called LouX^3D is applied to the non-destructive study of the Renaissance paintings series Famous Men, from the Louvre collection. Elemental depth profiles measured directly on the paintings are compared to lateral scans and results of conventional analyses on cross-sections removed from the paintings in the same locations. This comparison enables a better evaluation of the feasibilities of CXRF depth profiling using the LouX^3D set-up for the investigation of paint layers. The limit of depth profiling is reached due to absorption effects, which depend on the chemical composition of the paint layers, on their order and on the performance of the set-up. Care must be taken if the same element is present in adjacent layers, if the layers are thin (<10 μm), or if the composition within a layer is highly heterogeneous. Paint sequences on the original paintings, including later retouchings, were successfully detected using CXRF measurements. This study highlights the great potential of this laboratory-based method when used in combination with other techniques for completely non-invasive painting analyses.