The cleaning of paintings is carried out when an artwork legibility is jeopardized. This can be due to inevitable deposits on their surface or by a modification of the varnish optical properties as a result of ageing. For the most delicate restoration cases, laser processing was widely studied as an alternative to traditional techniques of painting cleaning. It encompasses two distinct approaches: the first one involves photo-thermal disaggregation of the unwanted material with an Er:YAG laser (2.94 μm) and eventually its chemical or mechanical removal while the second one involves ultraviolet laser ablation, generally with an excimer (193, 248 or 309 nm) or a high order harmonic Nd:YAG laser (213 or 266 nm). This study proposes a comparison of these two laserbased technique for removal of an urea-aldehyde resin, Laropal A81, widely used as a binder or varnish since the 90’s, but whose interaction with a pulsed laser was never studied. For this purpose, an Er:YAG laser (El.En LightBrush2 2.94 μm 500 mJ) and a 4th harmonic Nd:YAG laser (Quantel CFR 266 nm 50 mJ) were used. The cleaning procedure was monitored in both cases by optical microscopy, spectral domain-optical coherence tomography and UV-induced fluorescence. Results showed that both sources can give satisfying results when operated in optimal conditions.
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