FIBER OPTICS APPLICATIONS TO WORKS-OF-ART

In recent years physical and chemical investigations on works of art have significantly grown both for obtaining information on the materials and techniques used by the artist, and for developing useful guidelines on restoration. The main difficulty, which is encountered when precious and unique objects are examined, involves performing measurements in the safest way possible for the object. Therefore, we proposed, as the principal objective of our research, the development of totally non-destructive methodologies of investigation. Fibre optics reflectance spectroscopy (FORS), where fibre optics is simply used as an intrinsic optrode, is particularly suitable for our purposes, because it allows recording of reflectance spectra up to more than 2.0 mu m without any damage to the art work, and therefore offering the possibility of a large sampling. This last point is particularly interesting in comparison to the common microanalytic procedures, which, on the contrary, can only work on a few samples at a time. We used FORS as a powerful tool for: (a) pigment identification by means of a correlation analysis with a 'palette' appropriately prepared in a laboratory; (b) analysis of colour changes induced in paintings by the environment; and (c) documentation of the colour before and after restoration. As an example, we report the results of our investigations on paintings of the Middle Ages and the early Renaissance (Giotto, Masaccio, Luca Signorelli).