Scanning macro-XRF: Calculation of Sensitivity and Limits of Detection for common pigments in historical paintings and the investigation of Rembrandt’s ‘Saul and David’ .

Abstract

The aim of this research was to study and compare the potential of two mobile scanners MACRO-XRF, through the analysis of multilayered paint samples. Wood and plexiglass mockups were painted with some of the most common oil pigments in art, using a paint film applicator. Only wood samples were analyzed and covered by different thicknesses of lead white, in order to reproduce a real layers sequence frequent in historical painting. The two scanners MA-XRF were: M6 Jetstream, that is the first model of the production run by Bruker; and AXIL scanner, an in-house build scanner of the University of Antwerp. The potential of these two instruments was observed and studied through the change of some fundamental parameters: step size, dwell time and detector geometry. Qualitative considerations were based on elemental maps carried out by Datamuncher package. Furthermore, the best Instrument AXIL scanner set-up was used for quantitative analysis. In order to calculate meaningful data of sensitivity and limit of detection for each marker element, the dwell time was increased up to 2,5 second per pixel. The second part of this study shows a real application of AXIL scanner on Rembrandt’s painting “Saul and David” and the attention was focused on the different use of cobalt in the painting: as a pigment (smalt) or as a drier.