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 SO2 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:YVO4 laser working at 355 nm. It was concluded that the cleaning with mechanical procedures and laser was influenced by the SO2 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.