Medieval and renaissance glass technology in Valdelsa (Florence). Part 3: vitreous finds and crucibles

Optical, SEM-EDS and TEM microscopy, Mössbauer and UV–Vis spectroscopy, SIMS spectrometry and ICP spectroscopy, were carried out on sixty vitreous finds, with particular attention to the trace elements, in order to correlate them to the raw materials, the working instruments and the technology employed. The colours of these vitreous finds have been studied in detail to establish the presence and kind of chromophores, the redox conditions used for obtaining of the vitreous mass during the fusion process, the role of the oxidation state and chemical environment of the different metal ions, etc. Eight crucibles and one refractory material were also investigated by XRD diffractometry and TG-DTA thermogravimetry. Their composition, morphology and thermal behaviour gave information on the working temperature inside the kilns. These studies offer a scientific contribution to the archaeological requests to characterise correctly the pre-industrial glass manufactures in Valdelsa. The obtained results allow us to gain a more exhaustive knowledge of the production technology at Germagnana (14th century) and Gambassi (16th century) and of the provenance of the employed raw materials and to register differences and analogies in their production process.