GREGÓRIO LOPES painting workshop: characterization by X-ray based techniques. Analysis by EDXRF, μ-XRD and SEM-EDS

Gregorio Lopes is one of the most famous Portuguese painters of the 15 super(th)-16 super(th) centuries. This work is a contribution to the study of his painting technique, specifically addressing the methodology used in the preparation of ground layers, which has never been carried out previously with this multianalytical method. For this purpose characterization of the ground layers of a selection of his paintings was carried out by micro-Energy Dispersive X-ray Fluorescence spectroscopy ( mu -EDXRF), micro-X-ray Diffraction ( mu -XRD), Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS) and complemented by micro-Raman spectroscopy. This work presents the results obtained on two altarpieces (c.1544) produced at the same period by this Portuguese artist. Ground layers are composed mainly of calcium sulfate-anhydrite and gypsum-and other compounds such as dolomite. Reference samples were prepared to obtain diffraction pattern of different percentage of gypsum and anhydrite and compared with the results from historical samples.