Multi-Instrumental Characterisation Of Decorative Layers In Glazed Ceramic Reliefs From The Schwarzenberg Palace In Prague

This paper presents recent research results on glazes and ceramic bodies in glazed ceramic lunette reliefs from the second half of the 16th century. The main objective was to identify dyes in the coloured coatings and defects in the glazes using multiple instrumental techniques (X-ray fluorescence, portable X-ray fluorescence, X-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy and elemental SEM-EDS analysis, dilatometry and thermomechanical analysis). The research confirmed the presence of ionic dyes (Cu, Fe, Co, Sb, Mn ions) in medium lead glazes (approx. 28 - 63 wt. %), but also various types of yellow pigments in the Pb-Sb, Pb-Sn and the Pb-Sb-Sn systems were identified. Various defects were observed on the surface of glazes. In the case of the yellow glaze, the examination showed a lower lead content in the top layer. The defects - corrosion holes - were caused by selective corrosion in the environment of the waste pit. The green glazes in the lunette reliefs were damaged due to ageing of ceramics fired at low temperatures or due to irreversible moisture expansion of ceramic bodies.