Noninvasive Imaging and Spectroscopic Techniques Applied In Situ in Museums

Analysis of artworks inmuseums and galleries has become one of themost important features in conservation and restoration, and even in authentication and attribution, when doubtful. Materials applied by the artists, as well as painting techniques and procedures, have strong influence on the conservation state of an artwork, besides other historical and environmental agents. Many noninvasive techniques can be applied in order to know all these aspects, which should be applied as the first step in artworks analysis, prior to other invasive methods, which should only complement them, obtaining some more detailed results. Among the most used ones are UV-induced visible fluorescence (UVF) photography, infrared reflectography (IRR), and X-ray fluorescence (XRF) spectroscopy, with the latest developments such as macro X-ray fluorescence (MA-XRF) spectroscopy. UVF photography can show later interventions, IRR can reveal preparatory drawings and pentimenti, while XRF spectroscopy is used for elemental analysis of the materials applied. MA-XRF spectroscopy shows the distribution of chemical elements (and therefore pigments and possible changes in the composition) throughout the entire painting surface. All these techniques can be used directly in situ, in the exhibition hall or in the restoration workshop and without direct contact with the surface of the artwork. For security reasons, the study using X-ray must be done in an area closed to the public.