Production, mixing and provenance of Late Bronze Age mixed alkali glasses from northern Italy: An isotopic approach

Late Bronze Age glass in Mesopotamia, Egypt and Greece was made from silica and plant ashes. Around 1200BCin Europe a new glass type appears of a mixed alkali composition. Although the highest concentration of this glass is found at Frattesina in the Veneto, northern Italy there is no absolute proof that it was fused there from raw materials. A variety of possible alkali raw materials have been suggested but there is still no certainty about its identity. The chemical compositions of these mixed alkali glasses are characterised by a series of mixing lines which suggest that raw materials or glasses were mixed. To address these issues we present here the first set of radiogenic isotope (⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd) results for highly coloured samples of 11th century BCraw and waste glass from Frattesina together with new isotopic results for northern Italian silica and plant samples. Although a relatively small number, the isotopic results suggest that primary production of mixed alkali glass occurred in northern Italy. Moreover, it can be suggested that two of the samples were made from a mixture of different glasses, with contrasting isotopic signatures, one probably deriving from northern Italy and the other from a non-local source. This indicates that there were two production centres for mixed-alkali glass. We have shown that Frattesina glasses were made using isotopically distinct raw materials from those used to make the slightly earlier Late Bronze Age Mesopotamian and Egyptian plant ash glasses. Even though we have tested a small number of samples the isotopic results nevertheless provide significant new evidence for these mixed-alkali glasses being the first European glasses.