Medieval and Renaissance glass technology in Valdelsa (Florence). Part 2: vitreous finds and sands

A variety of green vitreous finds (fragments of worked objects, cuttings, moiles, fluidity test samples, glass masses, skims, and frits) from Germagnana (GE) and Gambassi (GP) sites, two glass manufactures of Valdelsa (Florence) have been investigated mainly by optical and scanning electron microscopy equipped with EDS, X-ray fluorescence, X-ray powder diffractometry, inductively coupled plasma atomic spectroscopy and, where possible, by Mössbauer spectroscopy in order to distinguish and classify them on the basis of their physico-chemical and/or mineralogical-petrographic properties. The mean composition of the different finds, their morphology, the included particles, the presence of crystalline phases, are reported. The role of the Fe(II)/Fe(III) ratio and of Mn in the production technology was estimated. Eight archaeological sands of the GP site were also investigated in order to verify their possible use as raw materials in glass production. The obtained physico-chemical and/or mineralogical-petrographic data corroborate the archaeological classification of the finds of the two Tuscanian sites and define more appropriately the glass production cycle and its evolution from the 14th to 16th century.