2Colour changes and reactivity to SO of some cladding stones at the “Gran Teatre del Liceu” (Barcelona; Spain)

This chapter describe the study conducted to select the most suitable cladding stones for the Great Theatre "Liceu" of Barcelona (Spain) from a series of pre-selected stones. It focuses on the color change and reactivity of cladding stones to sulfur dioxide (SO2). SO2 polluted atmosphere exposure was conducted because even very low atmospheric concentrations of SO2 can lead to decay of building stones. Six different stones were preselected: three light colored sedimentary and three dark colored metamorphic stones. In order to assist the final selection, these were subjected to a climatic chamber SO2 exposure. Although no visual color changes were observed, significant color changes were detected by colorimetric measurements. These changes were related to stone reactivity to SO2.