Production technology of Byzantine red mosaic glasses

The study of glass tesserae found in the excavations of the St Severo basilica at Classe, Ravenna, Italy, sixth century A.D., besides a comparison between these materials and those used for the decorations of the other churches of Ravenna built in the same epoch, has stimulated a discussion on the production technology of the red tesserae, which colour is due to the presence of metallic copper and/or cuprite (Cu2O) particles. As regards the opaque red glasses of the Iron Age, Roman and Byzantine periods, studies of English authors are particularly interesting, but the conclusions of the present study are partially in contrast with what reported in the literature that is based mainly on red enamels and much less on red mosaic glasses. For the studied Byzantine red mosaic glasses it is suggested the use of lead and lead-tin alloy scraps, besides additions of ash of the vegetal fuel, to attain the suitable reducing conditions during the melting process.