Mechanical and laser cleaning of spray graffiti paints on a granite subjected to a SO2-rich atmosphere

Abstract Cleaning effectiveness of four graffiti spray paints artificially aged by SO 2 exposure on granite was evaluated. Two different removal procedures were applied: i) mechanical methods with different micro abrasives (Hydrogommage® – combining action of air, water and micro abrasive-silica or aluminium silicate and IBIX® – combining action of air and micro abrasive-silica or calcium carbonate), and ii) a ns Nd:YVO 4 laser working at 355 nm. It was concluded that the cleaning with mechanical procedures and laser was influenced by the SO 2 exposure. Aged samples were more difficult to clean, suffering higher global colour changes. Hydrogommage® with silica abrasive achieved the best results, due to a combination of a satisfactory paint extraction and low morphological damages induced to the granite.