Towards the restoration of darkened red lead containing mural paintings: A preliminary study of the beta-PbO(2) to Pb(3)O(4) reversion by laser irradiation
Résumé
Red lead pigment darkening in paintings is generally caused by the pigment alteration into plattnerite (beta-PbO(2)). Plattnerite reversion into minium may be achieved by heating it over 375 degrees C. This reaction may occur by using continuous-wave (cw) laser irradiation. Laser-induced photo-thermal reduction of plattnerite into minium was investigated through irradiation tests on both pure plattnerite powder samples and darkened red lead paint samples taken from experimental wall paintings. The effects of both visible (514 nm) and near infrared (1064 nm) sources were investigated. This study shows the high potentiality of an innovative technique based on a continuous wave-laser irradiation for the restoration of darkened red lead-containing paintings.