Study of the effects of low-fluence laser irradiation on wall paintings: Test measurements on fresco model samples

• Published in: Applied surface science 2013-11, Vol.284, p.184-194
• Main Authors: Raimondi, Valentina, Cucci, Costanza, Cuzman, Oana, Fornacelli, Cristina, Galeotti, Monica, Gomoiu, Ioana, Lognoli, David, Mohanu, Dan, Palombi, Lorenzo, Picollo, Marcello, Tiano, Piero
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Cultural heritage; Exact sciences and technology; Fluorescence; Fresco wall paintings; Laser induced fluorescence; Laser irradiation; Lasers; Lidar; Optical fibers; Physics; Pigments; Spectroscopy; Texture; UV effects; Walls
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.07.077

•We prepared a set of model samples using pigments and a fresco technique.•We irradiated the fresco samples with low-fluence UV laser pulses (0.1–1mJ/cm2).•We analysed the effects of laser irradiation by using analytical techniques.•The analysis did not point out changes due to low-fluence laser irradiation. Laser-induced fluorescence is widely applied in several fields as a diagnostic tool to characterise organic and inorganic materials and could be also exploited for non-invasive remote investigation of wall paintings using the fluorescence lidar technique. The latter relies on the use of a low-fluence pulsed UV laser and a telescope to carry out remote spectroscopy on a given target. A first step to investigate the applicability of this technique is to assess the effects of low-fluence laser radiation on wall paintings. This paper presents a study devoted to investigate the effects of pulsed UV laser radiation on a set of fresco model samples prepared using different pigments. To irradiate the samples we used a tripled-frequency Q-switched Nd:YAG laser (emission wavelength: 355nm; pulse width: 5ns). We varied the laser fluence from 0.1mJ/cm2 to 1mJ/cm2 and the number of laser pulses from 1 to 500 shots. We characterised the investigated materials using several diagnostic and analytical techniques (colorimetry, optical microscopy, fibre optical reflectance spectroscopy and ATR-FT-IR microscopy) to compare the surface texture and their composition before and after laser irradiation. Results open good prospects for a non-invasive investigation of wall paintings using the fluorescence lidar technique.