Microstructure and stability of medieval glass bracelets from Drastar Castle, Bulgaria (11th–13th cent. AD): Four case studies

This paper discusses the microstructure and stability of medieval glass bracelets from 11th–13th cent. AD excavated in Drastar Castle, Bulgaria. All considered fragments represent high-magnesia soda–lime–silica glasses. Their chemical composition is determined by classical wet chemical analysis. Samples are investigated by infrared spectroscopy, X-ray diffraction and transmission electron microscopy. Softening points and water resistance are determined in order to establish the quality of glasses. The present study contributes to estimate the technological level of glassmaking during the Middle Ages.