The Gate of Paradise: Physical optimization of the laser cleaning approach

A methodology for the use of lasers in the restoration of the Gate of Paradise, a gilded bronze artwork by L. Ghiberti, was evaluated theoretically and experimentally. Preliminary characterization of the materials to be laser-cleaned made it possible to estimate the thermal regimes involved and to model the ablation process. Calculations aimed at controlling unwanted heating of the gold film were also developed before laser-cleaning tests on large areas were carried out. Finally, the cleaning tests were critically evaluated by means of instrumental inspection. The practicability of the laser approach, either as a preliminary to gentle chemical cleaning involving lower concentrations of chemical agents and shorter exposure times or as a standalone treatment, was demonstrated.