The apsidal stained-glass windows of Orvieto Cathedral: characterization of the materials

The apsidal stained-glass window of the Orvieto Cathedral is one of the most significant examples of this artistic technique in the Italian Gothic. Its restauration gave the opportunity to analyze the constituent materials, with special regard for the glasses and the leads. The use of a portable X-ray fluorescence system allowed a non-destructive global approach and reduced to minimum the number of samples for the scanning electron microscope observations. An important part of the investigations consisted in separing the original materials from the ones used in the restorations, carried out since the XIV century. In particular it was possible to identify characteristic compositional patterns in both the cobalt-coloured glasses and the XV century leads. Further investigations on the leads, carried out by SEM, proved the presence of a surface tin layer probably due to a peculiar soldering technique.