Thermal properties and microstructure of Roman flat window glass found in Bulgaria

The aim of this study is to carry out investigations in order to establish the composition and technological behaviour of the Roman glass dated from IV to VI c. For this reason the glass transition temperature (Tg) at 380 °C, the softening point at 490 °C and crystallization ability were determined. The fragment has been investigated by a classical chemical analysis, an electron probe microanalysis, differential thermal analysis, infrared spectroscopy, transmission electron microscopy and X-ray diffraction. According to the chemical composition, the fragment is soda-lime–silica glass that is typical for the production of this region. Microheterogeneities were found which are originated from the preparation method and from the corrosion caused by soil influence. As a result of additional thermal treatment the crystal phases were also established.