![]() KrF excimer laser at λ = 248 nm) where the functional groups of the varnishes and of their degradation products are strongly absorbing, while other types of lasers emitting in the infrared (Nd:YAG and Er:YAG ) have also been studied. The most exploited laser systems emit in the UV region (e.g. Its application as advanced tool for cleaning practices on paintings was introduced in the early 1990s and referred to the removal of aged/hardened varnish coatings, overpaints or soiling. Provided that the employed laser wavelengths are strongly absorbed by the material, their pulse duration is short and the fluence values are high, layer-by-layer material removal is feasible. ![]() Laser ablation is a complex process which refers to the interaction of a laser beam with a surface resulting in selective removal of small amounts of material. The combination of the results obtained by OCT and FT-IR complemented with those from LIF measurements are discussed with the aim of developing an efficient methodology for assessing in situ the irradiated painting surfaces after the laser cleaning treatments and, thus, setting the basis for a future monitoring scheme that would ensure optimum cleaning interventions.Ī physical method with continuously growing use in the cleaning practice of painting surfaces is laser technology. In parallel, laser induced fluorescence (LIF) spectroscopic measurements, recorded with the same laser beam at significantly attenuated energy density values, were exploited to provide information on the fluorescence properties of the irradiated varnish surfaces. A systematic integration of the information on the chemical changes of the molecular composition of the painting surface provided by reflection FT-IR spectroscopy with the visualization of the stratigraphical changes by OCT allowed the evaluation of the sensitivity of the painting materials to different operative parameters of the laser treatment, such as laser fluence and number of pulses. oxidized natural varnishes) and thus high selectivity and control of the cleaning process can be pursued. This specific laser radiation, operating in the ultraviolet region (λ = 248 nm), is highly absorbed by coating materials (i.e. waxes, aged natural varnishes, oxalates, deposition/migration compounds). ![]() Specifically, OCT and FT-IR analyses were carried out before and after each cleaning test in order to carefully assess the condition of the painting surfaces upon their irradiation with a KrF excimer laser and evaluate the removal of weathered and/or non-original materials (i.e. In the present study the potential of the combined use of optical coherence tomography (OCT) and reflection FT-IR spectroscopy for in situ non-invasive assessment of laser cleaning procedures has been investigated on a historical easel painting donated to science. discoloration, darkening, blackening) will occur on the painting surfaces due to laser ablation. The development of a non-invasive analytical protocol aimed at thorough assessment of the treated surfaces and real time monitoring of the laser cleaning action is thus becoming imperative. Nowadays the use of laser technology as a highly precise tool for the cleaning of paintings is gaining ground. Heritage Science volume 7, Article number: 44 ( 2019) Laser cleaning of paintings: in situ optimization of operative parameters through non-invasive assessment by optical coherence tomography (OCT), reflection FT-IR spectroscopy and laser induced fluorescence spectroscopy (LIF)
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