| Abstract: | SUMMARIES. 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 abla¬tion process. Calculations aimed at controlling unwanted healing 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 stand¬alone treatment, was demonstrated.
CONCLUSIONS. We investigated a safe laser cleaning methodology for the restoration of a number of sculptural ele¬ments of the Gate of Paradise. The optimization of the treatment, allowing avoidance of any mechani¬cal or thermal damage, was achieved through pre¬liminary irradiation tests and a detailed physical interpretation of the experimental observations aided by chemical analysis. The cleaning tests per¬formed on large areas demonstrated the applicabil¬ity of the developed methodology on the different surfaces and encrustation features of the sculptures to be restored. The laser treatment also increased our understanding of the artwork under restoration because of the specific interaction of the laser with the materials of which it is composed. However, we cannot rule out other peculiarities of the encrusta¬tion distribution and composition, calling for addi¬tional research to improve the technique and better characterize the state of preservation and the histor¬ical issues related to the art object. The main advantages of an optimized laser methodology are that it makes it possible to clean the sculptures without the dangerous mechanical dismounting from the framework, and that it avoids or at least limits the use of reactive chemical agents. In collaboration with the team of experts from the OPD we will perform further studies aimed at comparing the results of the laser method¬ology we have presented with those obtained using an integrated approach combining laser ablation and the use of chemical poultices with lower con¬centrations of active agents. |
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