Analyses of vessel glass fragments from the Byzantine church of transfiguration of the saviour in Metamorphosis, Messinia, Peloponnese

Abstract

Thirteen glasses from the Byzantine Church of Transfiguration of the Saviour in Metamorfosis in Messinia, Peloponnese, dating back to the Middle Byzantine Period (12th century A.D.), have been analyzed. The methodology adopted aimed to identify the chemical properties of the glasses and the methods used were the following complementary techniques: Optical Microscopy (OM) for preliminary morphological observations, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectrometry (SEM-EDS) for high-resolution morphological examination and qualitative chemical analyses and Micro X-ray Fluorescence Spectrometry (μ-XRF) for the detection of trace elements. The chemical characterization of the glasses allowed the discrimination between different glass groups and the identification of raw materials and technological traditions of their production. Fundamental changes in the production processes occurred from the 8th-9th century A.D. onwards, when mineral soda was gradually replaced by organic plant ash. These changes in the raw materials are reflected in the chemical composition of the glasses. The major components of the glasses are silicon dioxide (SiO2), sodium oxide (Na2O), and calcium oxide (CaO) and the samples can be classified as soda-lime-silica glass. Most of the fragments revealed an intermediate composition a combination of natron and plant ash glass. Among the samples a glass composition with a certain amount of plant ash was also identified, an indication of a new glass composition introduced after several centuries in which natron glass was dominating glass production. Micro X-ray Fluorescence Spectrometry (μ-XRF) results highlighted the elements responsible for coloring and indicate the possibility for the glasses to be obtained through recycling processes, clarifying production technology issues. Finally, it is possible to assume as the source of the raw glass to have been the Middle East.