In the church, the samples attest a technological change from Roman tradition, and a complex pattern according to building history (two phases are attested, probably in the sixth and eighth to ninth c.), and a multiplicity of supply. They were made using a Levantine 1 raw glass, generally attributed to the early Byzantine period (fifth to sixth c.). In the destruction layers of the theatre, tesserae produced following the Roman glassmaking technology (natron glass opacified by calcium and lead antimonate) were found. The aims are to add new information to the scant knowledge of the Byzantine glassmaking technology, to constrain the chronology of the mosaics and to trace the supply routes of the tes-serae. Philip) are analysed by particule-induced X-ray emission and particule-induced gamma ray emission and electron probe X-ray microanalysis to obtain the chemical composition and identify the colourants and opacifiers. Fifty-seven samples of loose tesserae from two sites in the town (the theatre and the church of St. This study focuses on the Byzantine glass tesserae from Hierapolis (Phrygia, central Turkey). The results demonstrate that good quantitative analyses of the metal leaf can be performed and that metal leaves made of pure gold or goldsilver alloys were used. The comparison of the composition of the gold leaf of the tesserae with that of circulating gold coins (for which an important analytical data base is available), adds further information to the glass analysis, allowing us to improve the dating of the tesserae and increase the knowledge that may result from scientific analyses. The SEM-EDS analysis is proposed in this study as a useful tool to investigate the composition of both the glass and the gold alloy in leaf tesserae from mosaics of the 1st - 9th centuries. Available information is still scanter for glasses produced between the 1st to 8th centuries when the batch of raw materials (a natural soda called natron and a silica-lime sand) was melted in large tank furnaces and chunks of raw glass were transported all over the Mediterranean to be remelted and shaped into manufacts in small pot furnaces. The determination of the glass composition of the tesserae is not of great help in this connection, for the same kind of glass was used over long periods. From an archaeological point of view, it is interesting to know when and where these tesserae were made, if they were new made or if they were reused tesserae recovered from earlier dismantled mosaics. According to various techniques that have changed over the centuries, the leaf was hot fixed between two glass layers. The metal leaf could be obtained from circulating coins, jewellery or refining. Metal leaf (gold, silver or their alloys) glass tesserae began to be used in wall mosaics in the first century AD (the first examples are in Rome) and their use has been uninterrupted up to day.
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