Browsing by Author "Adam, Karin"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Primary stabilization factor of the corrosion of historical glasses: the gel layer
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Müller, Wolfgang; Torge, Manfred; Adam, Karin
    Leached gel layers of variable thickness and composition, mostly crisscrossed by cracks and fissures, are built during long term exposure of historical glasses. Depending on the glass composition as well as on the environmental conditions the gel layers show various shapes. They can be characterized by microprobe investigations, through photographs of the cross-sections in vertical plane to the corroded surface as well as determination of the chemical composition. Any cleaning measures in the course of restoration have to obey carefully their preservation, for it seems quite reasonable to assume that the progress of corrosion of the poorly resistant glasses is remarkably retarded by silica gel barriers.
  • Thumbnail Image
    Item
    Ratio of CaO/K20 > 2 as evidence of a special Rhenish type of medieval stained glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Müller, Wolfgang; Toge, Manfred; Adam, Karin
    The chemical compositions of more than 300 medieval stained glass samples of different local origin have been published so far. Regarding their characteristic components they can be classified into five types. About 80 % of all investigated samples proved to be potash-lime-silica glasses with roughly equal concentration of CaO and K₂O (type 1). But a small group of little more than 20 samples gave a ratio of CaO/K₂0 > 2 (type 2), all but three of which had been taken from two churches of the Rhine region (St. Catherine Church Oppenheim and Cologne Cathedral). Hence, it seems likely that a corresponding recipe was used there, which was nearly unknown elsewhere in Europe. Investigation of further objects of this region might be of interest for the history of technology.