PROMOTE · The provenance of mosaic tesserae: an interdisciplinary study on Roman Age glass production and trade in Italy

The provenance of mosaic tesserae: an interdisciplinary study on Roman Age glass production and trade in Italy

The PROMOTE project investigated the problem of the provenance of Roman glass mosaic tesserae, used in mosaics from Italy, during the period late second century BC-late second century AD. The methodology adopted is strongly interdisciplinary and it is focused on the integration of the archaeological fieldwork with the analytical characterisation of glass samples, applying innovative scientific methodologies, such as the analysis of the isotopes, to trace the provenance of the raw materials used to make the glasses. The main results of the project can be summarised in three major accomplishments. 1. The observation of wall and floor mosaic yielded the creation of a chronology of the vitreous materials used by the mosaicists between the end of the second century BC and the early second century AD. Some vitreous materials were only used for a short time and their identification provided the opportunity to date mosaics of uncertain date. 2. A work protocol was designed and tested in the laboratory in order to perform successfully the characterisation of the glasses. This protocol is based on the principle of choosing the analysis in order to solve archaeological problems and giving priority to the application of non destructive and micro-destructive techniques. The work protocol can be summarised using the following points: a. literature research and observation of mosaics during fieldwork (result: collection of samples); b. description of the samples (result: creation of groups by non analytical criteria); c. non destructive microstructural and compositional analysis (result: first creation of groups by analytical criteria, i.e. distinction by opacifier; plant ash or natron glasses; lead or non lead glasses); d. micro-destructive and non destructive trace element analysis (result: second creation of groups by trace element composition); e. micro-destructive lead isotope analysis (result: creation of groups by lead isotope signature); destructive strontium (Sr) and neodymium (Nd) isotope analysis (result: third creation of groups by Sr and Nd isotopic signatures). 3. The last accomplishment, corresponding to the completion of the major aim of the project, derives from the interpretation of the lead, strontium and neodymium isotope analysis. The analytical investigation, applied to Roman glasses and possible raw materials (carefully selected from specific geological sources), clarified that the glasses used in Italy as Roman mosaic tesserae are, according to the values of the isotopes, comparable to the raw glasses and the glass vessels that circulated in the peninsula at the time. The materials analysed dating to the second BC to the second AD fall into restricted groups, providing the hypothesis that there were few production centres, active for at least four centuries. The tests conducted on opacified and non opacified glasses showed that, in the period considered, the phenomenon of recycling the glass probably did not occur for mosaic glass tesserae. The lead isotope analysis showed that the lead used as raw material to opacify and colour the glasses derived from metal mainly circulating on the Mediterranean market during the period analysed. The provenance of the lead generally does not match the provenance of the sands used to make the glass. The impact of the project can be measured in term of scientific results and training activity. The project produced highly innovative data that contributes in a meaningful way to a better understanding of the topic. The interdisciplinary methodology developed for the study of mosaic tesserae will and can be applied to other glass artefacts, belonging to different historical periods. The researcher had the possibility of expanding her management and networking skills, developing research activity over two years and communicating with scholars from different academic backgrounds. The dissemination of the results in seminars and conferences by presenting and discussing the accomplishments of the PROMOTE project has helped the researcher to integrate within the European scientific community.

Data: CORDIS, © European Union