Laser cleaning of stones: assessment of operative parameters, damage thresholds, and associated optical diagnostics

After a general discussion about the optimum laser pulse duration for laser cleaning of stone artworks, we present a basic study aimed to state a methodological approach to optimize restoration interventions. As representative examples we investigated the cleaning problem of black crust removal from pliocene sandstone and marble of Siena. The trials were performed with a shot free running Nd:YAG on quarry samples, and on sample from historical buildings. Optical and thermal analyses, associated with petrological diagnostics of the irradiation effects, allowed to derive the damage thresholds and to understand the nature of any invasive phenomenon. The analysis of the experimental results provided the best irradiation conditions and the laser parameter ranges for a safe laser cleaning intervention of the lithotypes and degradation typologies here investigated.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.