Determination of damage thresholds to prevent side effects in laser cleaning of pliocene sandstone of Siena

The present work reports a basic investigation aimed at optimizing lasercleaning interventions on pliocenesandstone of Siena. Irradiation trials were performed with a short free running Nd:YAG laser, on quarry samples and on samples from Palazzo Spannocchi presenting black crust. The physical parameterization associated with a detailed petrographic and mineralogic diagnostics of the induced effects, allowed the irradiation thresholds for damage phenomena to be derived and their nature understood. The experimental results reported here allow the definition of the best irradiation conditions and the laser parameter ranges for a safe and controlled black crust removal from pliocenesandstone.