Ion beam and infrared analysis of medieval stained glass

Ion beam analysis and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize 15(th) century stained glass fragments from Batalha Monastery. This information is being used to help establish their origins as well as the art schools and artistic trends involved in the manufacture of these panels. As the preservation of art objects and artefacts is a major issue, the combination of Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) with FTIR spectroscopy aims at determining non-destructively the elemental compositions of the bulk glass and painted layers as well as identifying corrosion products. Elemental spatial distributions were obtained with a nuclear microprobe, and compared with the results of micro-FTIR. Although the bulk composition determined is consistent with the glass manufacturing practices of the Middle Ages, the grisailles were found to have a significant Zn concentration, at variance with those same reported practices. The analysis also revealed a surface layer impoverished in Si and K and enriched in Ca. That may be due to the migration of Ca ions to the surface, a known glass corrosion process consistent with the presence of CaCO3, as indicated by micro-FTIR.