CHARACTERIZATION OF LASER CLEANING OF LIMESTONE

The precise and controlled cleaning of polluted limestone sculpture by a Q-switched Nd:YAG laser is described. Acoustic monitoring of the cl eaning process is used to demonstrate the selective removal of black c rusts from stone surfaces. Results are also presented which show that by applying a thin layer of water to the surface of the crust prior to irradiation, cleaning can be achieved at a lower energy than with nor mal laser cleaning. The probability of damage to the underlying stone is, therefore, reduced.