Optimization of the laser cleaning of rough surfaces of granitic stones used in the building heritage of NW Iberian peninsula

Granite is the most common building stone in the NW Iberian Peninsula. As marble, granite exhibits crusts and patinas caused by its interaction with atmospheric agents and with biological activity [1]. Thus, the main conservation intervention is the cleaning. In the last years, laser ablation has been one of the most studied cleaning procedure and it has been proved more complex in case of granite than in other stone materials (i.e. marble) because of its polymineral composition, which leads to different responses under laser irradiation. In previous works, the effectiveness of various laser equipment has been found different considering the coating nature and the granite type, i.e. mineralogy, texture and especially surface roughness [2]. Therefore, it is necessary to carry out a study of the influence of the surface roughness on the laser cleaning effectiveness.