Corrosion stratifications on glass jewellery excavated beneath the market square in Kraków, Poland

Glass has been one of the materials selected for its decorative purposes since early mankind. Its production was complex and varied all around the world, considering the sources of local materials used for its production as well technological knowledge about the manufacturing process. The aim of this work is to put some light on glass jewelry unearthed during the archeological excavations at the Main Market Square in Kraków, and to increase the importance of a stratifications investigation of ancient subjects by induced corrosion, using glass sensors. The collected data helps to determinate the definitive condition of a historical object. This data will also help to establish the chemical nature of the corrosion products and the altered glass and metal surfaces. Moreover, the ring presented in this work can be considered to be from a small group of fine medieval jewelry corresponding to the upper class of the population, such as the nobility or wealthy merchants. Such individuals dealt with the exchange of goods with foreign countries. Because of a very limited amount of analytical material, only nondestructive analysis: scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), glass sensors were applied. The glass and metal have been tested separately.