Different glassmaking technologies in the production of Iron Age black glass from Italy and Slovakia

This study presents the results of an archaeometrical investigation performed on 75 black glass beads dated to the ninth–fifth century BC coming from Bologna, Cumae, and Pozzuoli (Italy), and Chotin (Slovakia). The analyses of the major, minor, and trace elements—as well as that of Sr and Nd isotopes performed on a selection of samples coming from Bologna—provided evidence for two different production technologies in Iron Age black glass found in Italy (natron glass, probably produced in Egypt) and Slovakia (wood ash glass, probably produced in Europe). In both cases, the glasses derive their black colouration from the high presence of iron (around 12 % FeO), introduced into the glass batches through the intentional choice of dark sands. The production model appears to be small-scale and experimental, characterised by the use of non-sorted raw materials and poorly defined formulae, producing glass with a high chemical variability. The wood ash technology appears to have dropped out of use in Europe until the Medieval period, while natron production spread quickly, becoming predominant throughout the Mediterranean.