Two new mechanisms for laser cleaning using Nd:YAG sources

Two new methods for the laser cleaning using a Q-swihed Nd:YAG laser have been developed and investigated. These offer increased efficiency and reduction in possible substrate damage for a wide range of substrate/encrustation combinations. In angular laser cleaning, it is shown that by controlling the angle of incidence of the cleaning laser, significant improvement in the efficiency of cleaning can be achieved when compared with conventional cleaning with a normal angle of incidence. A model is proposed to explain this effect. In laser shock cleaning, a completely different approach is presented. By aligning the incoming laser beam to be horizontal to the surface to be cleaned but close to it and selecting operating parameters that lead to a breakdown of the air above the object to be cleaned, a laser-induced shock wave is produced that is very much more effective than conventional normal incidence cleaning in removing surface pollutants. However, because the laser does not come into contact with the substrate, this method significantly minimises the potential for substrate damage. Again, a model for the cleaning process is presented. The results for the operation of both methods on polluted marble are presented. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.