The glass of Nogara (Verona): a "window" on production technology of mid-Medieval times in Northern Italy

The site of Nogara (province of Verona, Italy) provides valuable insights into the complexities of the glass industry in mid-Medieval times, due to its timing, which ranges mainly between the 10th and 11th centuries AD, and to the great quantity of glass findings, mainly tableware. In the present paper, the combination of archaeological, chemical and textural data allows us to identify production technologies in a time-interval perceived to be a period of technological transition for glass. In particular, the frequent occurrence of recycled natron glass and only a few glass samples made with soda plant ash indicate that recycling of earlier glass was common in inland Northern Italy in the 10the11th centuries AD. In addition, blue and reticello decorations were obtained by recycling earlier glass mosaic tesserae, as shown by much Co, Cu, Sn, Sb and Pb and the presence of crystallised calcium antimonates. A few glass samples with chemical compositions intermediate between natron and soda plant ash glass were also identified, suggesting a gradual change in glass composition from natron-based towards soda ash-based production technology, which prevailed in the 13th-14th centuries. In conclusion, the difficulty in describing mid- Medieval glass as a well-defined entity, due to the great propensity for recycling earlier glass samples which causes variability in chemical compositions, particularly those of trace elements, is clearly documented here. In any case, this paper contributes to a new type of chrono-typological scanning and to more detailed knowledge of glass production technology during mid-Medieval times in Northern Italy, little found in the literature until now.