Deterioration of building ceramics by environmental factors - a case study on Zsolnay ceramics from the museum of applied arts (Budapest)

Nowadays much more attention is being paid to the influence of mankind on our environment than previously. The expansion of urban conglomerations and the developing industry has resulted in an increased amount of aggressive pollutants [1]; therefore in the 21st century one of the major roles of society is to conserve its historical and cultural heritage. Pollutants from transport, heating and industry deposit on the built environment, causing its deterioration. Deterioration of natural building materials, like stone (e.g. freshwater and coarse limestone), is subject of numerous studies [e.g. 2], however few studies are designed to research the effect of air pollutants (e.g. sulfur dioxide, nitrogen oxides, soot, dust) on man-made silicate-based materials (ceramic, glaze, glass etc.). In Budapest there are many examples of historic buildings covered with glazed ceramics (e.g. the Museum of Applied Arts, Parliament, the Geological Institute and Matthias Church). It is widely accepted that, as Tournié and Ricciardi state, “the high melting temperatures of ceramics and glasses implies that diffusion coefficients of most of the elements are too low at ambient temperature to be significant at human lifespan and these materials are often considered to be corrosion resistant” [3]. However the air pollutants derived from different sources can damage ceramics and glasses easily if these silicate-based materials are exposed for a long time to the harmful factors. The most important reactions are dissolution of ceramic, glass and glaze, material transport to the contacting meteoric water or moisture, formation of new phases on the surface of the weathered object (so-called “hydrated silica” layer) and appearance of cracks/microcracks on the surface [3]. Our purpose is to reveal the effects of air pollutants on building ceramics (glazed ceramic roof tiles and decorative items) that originating from the Museum of Applied Arts, Budapest. In order to determine the deterioration mechanisms, we have examined the phase composition and the microfabrics of the ceramic body and the glaze, and studied the depositions accumulated on the surface of the ceramics.