Achaeometrical Research in Hungary II., 1988

ANALYSES - GLASS - Edit MESTER - István SZABÓ: Research of medieval glass vessels and glasshauses in Visegrád and Diósjenő

3. Material studies of glass finds from the Royal Palace of Visegrád The aims of research described in this chapter was to find and apply analytical methods for the identification and testing of glass samples excavated at various places in Visegrád. The compositions of glassware were determined by destructive chemical analysis and by means of inductively coupled plasma spectrometry (ICP-OES) using equipments and crystallised components in a few samples of weathered and heat treated glasses. X-Ray Diffraction (XRD) studies were carried out using the Debye-Scherrer powder method and filtered Cu Кос-radiation. Small pieces of glass samples were ground to a fine powder and mounted in a Philips camera (type PW 1820) before and after the heat treatment (1000 °C/10 min). The resulting diffraction patterns were identified by means of the ASTM powder diffraction file and card index. Differential Thermal Analysis was performed employing a DTA type of Paulik-Erdey Analyser with an operating capability in air to 1000 °C. The glass sample was contained in a corundum crucible. Alumina was employed as a reference material. The data were recorded by means of a chart, in which values of temperature were measured manually. The cross section of the broken glass samples and their surfaces were examined using a JEOL JSM-50 A Scanning Electron Microscope (SEM) working with 25 kV potential, in Secondary Electron (SE) mode and equipped with an Energy Dispersive X-Ray Microanalyser. All samples from Visegrád were found to be soda glasses (Fig. 4). The fine, clear (Fig. 2, No. 4-9.) and the palish green (No. 1-2.) glass samples had a thin iridescent layer on their surfaces. In the case of the second group of samples, the pieces of dark brown glass (No. 3.) were pitted and crusted. The Na

2

0 content (composition expressed in molar percentages) increased from 9.8 to 12.7, except for sample No. 3. which had an unusually high Na

2

0 content (19.43) and contained only 0.11 K

2

0. The K

2

0 content in the first group of samples varied between 2.17 to 7.17. The MgO and CaO contents changed from 1.01 to 8.38 and from 10.05 to 14.78, respectively. In the case of Sample No. 3, the concentrations of MgO (5.0) and CaO (11.32) are of medium level. Data for individual pieces Fig. 2: Compositions of glass finds listed above a triangular diagram (E. MESTER, I. SZABÓ, 1997.) of glass within samples were published elsewhere. 100