The ancient glass production of the Medieval Val Gargassa glasshouse: Fe and Mn XANES study.

Glass finds from the Medieval Val Gargassa glasshouse (Genova,Italy) were investigated by chemical and spectroscopic techniques (colorimetric analysis and X-ray absorption spectroscopy) with the aim to obtain information on the ancient glass production technique. Sampling covers all the typologies of archaeological findings unearthed by the digging,as well as fragments of finished glass-wares. The results indicated that the samples are soda-lime based glasses. The color variability was exerted by the glassmakers by both controlling the kiln atmosphere and/or adding MnO2 as decoloring agent. In both cases,the Fe2+/Fe3+ ratio was modified at a specific step of the production cycle