Portable equipment for energy dispersive X-ray fluorescence analysis of Giotto's frescoes in the Chapel of the Scrovegni

Photon induced energy dispersive X-ray fluorescence (EDXRF) analysis is a valuable technique for the study of works of art, because it is nondestructive, multielemental, simple and relatively inexpensive. For this reason EDXRF is a very popular analytical technique in archaeometry. Portability of EDXRF equipments is extremely useful and almost mandatory in many cases, such as analysis of frescoes, of large paintings, bronzes, brasses and gold alloys, and so on, especially when located in museums. EDXRF analysis generally involves an area of a few mm2, and a thickness between μm and fractions of mm and, therefore, the analysis is superficial and dependent on the surface conditions. The frescoes by Giotto in the "Chapel of the Scrovegni" in Padua were systematically analysed in the period July 2001-March 2002 in more than 300 points, before, during and after restoration, in order to detect the possible presence of superficial sulphur and to test various sulphur cleaning procedures. Further all pigments were systematically analysed in order to determine their composition. Golden haloes were also analysed and different pigment layers were detected under the gold leaf; from the EDXRF analysis the attribution of chemical elements to the proper layer was possible.