Glass fragments from the Crypta Balbi in Rome: The composition of eighth-century fragments

Eighth-century glass fragments from the Crypta Balbi in Rome were analysed by inductively coupled plasma emission spectroscopy. The samples included fragments of artefacts as well as ingots of raw glass and wasters. All the fragments proved to be soda-lime glasses. Manganese-to-iron atomic ratios are highly variable and determine the colour of a large number of samples. Fairly high copper contents, generally associated with relatively high amounts of antimony and lead, were detected in some green and blue-green samples: this suggests recycling of glass in the form of opaque mosaic tesserae. All three elements are higher in eighth-century than in previously analysed seventh-century fragments. This may indicate greater recourse to recycled glass, related to a reduction in trade exchanges in the Mediterranean.