Principles and applications of XRF analysis with portable equipment

Abstract

Since about half a century X- ray fluorescence (XRF) is a key technique for the investigation of cultural materials. The reasons of its success are at least three: a) it performs elemental analysis, which is essential for the identification of the object's component materials, as well as its provenience and fabrication technologies; b) it is non- destructive, where the analysed objects are in most cases unique and artistically relevant and c) the equipment can be made portable and therefore used inside museums or conservation laboratories on objects that often are too big or too fragile to be moved. With a special regard to portable equipment, this paper discusses general aspects of the XRF technique, such as its range and methodology of use. The particular efficacy of the spectrometer at performing a rapid preliminary selection of materials to be subsequently investigated with more sophisticated techniques is highlighted. Finally three case studies concerned with copper alloys are presented: the byzantine door of the Basilica di San Paolo Fuori Mura in Rome, a group of artifacts from Deposito de Trèstina and the Late- Roman coins of the Misurata Treasury. In the study of these objects, it is shown how it was possible to obtain in a non- destructive way important data concerning the characteristics of some parts of the original structure of the mentioned pieces, although quantitative measurements were not carried out. That is particularly true for the Roman coins, about which the analysis has provided the base for important historical studies that brought new and relevant information concerning the period's monetary policies.