Compositional and Morphological Investigations of Roman Glass from Cremation Deposits at Birdoswald Fort on Hadrian’s Wall, UK

Abstract

Several different types of burial were identified during the excavation of the Roman military cemetery associated with the fort at Birdoswald, on Hadrian’s Wall (UK). Fragments of glass vessels and glass beads were recovered from many of the cremation deposits, as they were commonly used during cremation rituals, and many of these had been affected by heat. X-ray fluorescence spectroscopy and scanning electron microscopy were used to investigate the raw materials, colorants and opacifiers employed to produce the glass assemblage. Most of the large fragments are transparent with a blue-green colour, with a composition typical of recycled glass. The smaller fragments are from beads and are coloured and sometimes opaque. Colourants and opacifiers characteristic of Roman glass were added in this glass formulation, including cobalt-based compounds (blue glass), copper alloys (green glass), white calcium antimonate, and yellow lead antimonate. The multianalytical approach of this research has allowed for the distinguishing of the extreme depletion of sodium on the surface of the melted glass fragments due to the exposure to high temperatures during the cremation process, followed by surface weathering in a burial environment. Based on the chemical composition of the bulk of the samples, a model of high temperature viscosity of glass was applied in order to assess the cremation temperature in the pyre, providing relevant information about funerary rituals and cremation technology in Roman Britain.