Testing and evaluation of laser cleaning of a varnished 20th century oil painting

This article presents the development of a cleaning methodology for twentieth-century varnished oil paintings using Er:YAG lasers emitting 2.94μm pulses. The study evaluates the Er:YAG laser efficacy to safely reduce thin varnish layers on such paintings. Tests under single and multiple laser pulses, fluences ranging from 0.56 J/cm2 to 2.40 J/cm2, on dried and wetted surfaces of the painting were carried out by applying polar and apolar solvents. Glass coverslips were placed on the painting during irradiation to collect the ablated fragments. Principal component analysis maps of multispectral images of the treated surface indicated the efficiency of the procedure. Further evaluation was performed by optical microscopy and colorimetry.