The laser as a tool for the cleaning of Cultural Heritage

Laser ablation is one of the most important irradiation effect which can be induced on optically absorbing materials. Laser cleaning is a particular case of laser ablation where a specific substrate is uncovered through the removal of undesired layers. The idea of using laser ablation for the selective removal of encrustations from the surface of artifacts dates back to the 70s. However, only in the last years, thanks to studies on the ablative process and on the development of dedicated laser systems, laser cleaning has become a daily routine in the world of conservation. The development of brand new devices optimized for the cleaning of artworks is here reported: the innovative machines exploit the versatility provided by the presence of different pulse durations, which turned out to be a key parameter in the laser-target interaction. In addition to the well-known laser cleaning of stones, novel applications are discussed such as the cleaning of metals, wall paintings, and the novel use of the Er:YAG laser for the removal of aged varnishes from easel paintings. The growing flexibility and versatility of the new laser systems dedicated to the cleaning of artworks enlarge the panorama of successful application of this cleaning method.