On the study of paintings' stratigraphy by fs-LIBS and MA-XRF techniques

Abstract

Works of art, especially paintings, often involve successive layers of materials of diverse compositions and properties. The current study explores the potentialities of the combination of femtosecond Laser Induced Breakdown Spectroscopy (fs-LIBS) and Macro X-ray Fluorescence (MA-XRF) for the study of paintings. In this framework, two mock-up samples that were manufactured by using traditional post-byzantine painting methods and numerous inorganic and organic pigments was thoroughly investigated. The selected pigments were either applied as single paint layers on top of a calcium carbonate substrate or as a combination of two and/or three successive paint layers over the substrate. The authors attempt to disclose the layered structure of the paints by inspecting some carefully chosen LIBS spectral features (markers) as a function of the laser shot number. The various paint layers are identified by applying less than ten laser shots while the diameter of the induced craters is limited to under 100 μm. Additionally, it is shown that through the proper treatment and evaluation of complementary MA-XRF data, one may overcome some of the fs-LIBS limitations and thoroughly investigate a painting's stratigraphy. Given the micro-invasive character of fs-LIBS and the non-invasive character of MA-XRF, combining the selected analytical methods is a promising tool for painting investigation.