Comparison between destructive and non-destructive quantitative chemical analyses of glass mosaic tesserae

A very useful non-manipulative and non-destructive analytical technique for in situ investigations in the cultural heritage field is the X-ray Fluorescence (XRF) portable spectrometer. This technique has been successfully employed in the analyses of various type of materials but up to now only few application have been found on the use of portable XRF for the analyses of glasses and obsidians due to the limit of the technique in the detection of the light elements (typically Na and Mg). In this work we have checked the applicability of this technique for the quantitative analyses of a set of mosaic tesserae by comparing the data obtained by the XRF portable spectrometer with those previously obtained by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) on a set of mosaic tesserae from S.Vitale in Ravenna. This is a laboratory test to be developed in an in situ analytical protocol at use and advantage of art historians and conservators for their “first-sight” knowledge of the mosaic glass characteristics.