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The present work focuses on the potential of 3D digital microscopy for assessing micro-morphological features during laser cleaning treatments of artworks. This application requires preliminary optimization studies aimed at defining operative irradiation parameters and practicable degree of cleaning, as well as in situ diagnostic assessments during the restoration work. To this goal, we developed and tested a dedicated 3D digital microscope by implementing the 'shape-from-focus' technique. The significant potential of this instrument, which provides textural and chromatic information, was proven for the phenomenological characterization of black crust removal from stones, earthy concretion from bronzes and dark varnish from easel paintings. Comparative measurements using 3D digital microscopy and contact microprofilometry were performed after laser cleaning tests of prepared samples, genuine archaeological bronze artefacts and a stone sculptural element from Florence's Dome. The results achieved demonstrate the effectiveness and reliability of the novel approach and the advantages it provides with respect to alternative techniques, which will allow the methods to be used in the wider restoration community. [ABSTRACT FROM AUTHOR]

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 in involving lower concentrations Of chemical agents and shorter exposure times or as a standalone treatment, was demonstrated. [ABSTRACT FROM AUTHOR]