UNIQUE PRE-ROMANESQUE MURALS IN KOSTOLANY POD TRIBECOM, SLOVAKIA: THE PAINTING TECHNIQUE AND CAUSES OF DAMAGE

Pre-Romanesque murals at Kostoany pod Tribeom, Slovakia, have been investigated by portable X-ray fluorescence and by microanalytical methods to identify painting materials (pigments and binders), and to explain the degradation of colours. Today, missing green and blue shades have been reconstructed according to residual concentrations of Cu, which correspond to copper chloridesproducts of salt corrosion of the copper carbonates azurite and/or malachite, accelerated by micro-organisms. As confirmed by powder X-ray microdiffraction, original minium (Pb3O4) has been transformed to brown-black plattnerite (PbO2). In increased humidity, even insoluble pigments are washing down from the walls and the intensity of colours further diminishes.