Fragments of luxury: Opaque glass from the Palace of Mystras, Greece

Abstract

The present study focuses on the analysis of nine opaque or translucent glass samples of white, grey/blue and red colour, recovered from the Palace Complex of Mystras in southern Peloponnese, Greece. Their date cannot be determined with specificity but has to span between the mid-13th and mid-19th c. AD, the period since the construction of the site and throughout its continuous use as the administrative centre of the Despotate of Mystras. The extremely rare occurrence of opaque glass vessels of this period in Greece, as well as the recovery of most samples within Building E of the Complex, suggest that the samples were precious objects, possibly owned by high ranking members of the Palace. A multi-technique approach, including Optical microscopy, SEM/EDS, Raman spectroscopy and TEM analysis, was implemented in order to determine the microstructure and raw materials of the samples.Despite the small number of samples, a remarkable variability was revealed in terms of the raw materials and manufacturing processes employed. Overall, three different opacification techniques were documented among the white and grey/blue samples: The Na-rich glasses were opacified using either cassiterite, a typical opacifier for the period, or calcium antimonate, a less common opacifier in the post-Medieval glassmaking. The K-rich white glasses were opacified with the addition of the ashes of animal bones, as suggested by the presence of calcium phosphates, a Byzantine tradition that was possibly also used by Bohemian glassmakers.Finally, the red glasses present certain atypical traits in their microstructure and chemical composition. The samples contain multiple calcite, tin oxide and lead oxide particles. The colour is due to copper, which could only be identified with the application of TEM analysis, in the form of copper oxide nanoparticles.The present study highlights the complicated traditions employed for the production of opaque glass in the post-Medieval European workshops and it underscores the need for a more thorough study of related material.