Effect of low and high fluence on experimentally laser-cleaned sandstone and marlstone tablets in dry and wet conditions |
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| Institution: | 1. School of Art Restoration, Academy of Fine Arts, U Akademie 4, 170 22 Prague 7, Czech Republic;2. Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic;1. Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country, P. K. 644, 48080, Bilbao, Spain;2. Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Matériaux, CNRS UMR 5254, Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2, av. P. Angot, 64053, Pau cedex 9, France;1. Department of Civil and Environmental Engineering, Stanford University, USA;2. Department of Civil Engineering, Indian Institute of Technology Delhi, India;1. Wuhan National Laboratory for Optoelectronics (WNLO), Huazhong University of Science and Technology (HUST), Wuhan 430074, China;2. School of Optical and Electronic Information, Huazhong University of Sciences and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, China;1. Department of Chemistry and Bioactive Material Sciences and Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 561-756, Republic of Korea;2. Department of Chemistry, Dankook University, 152 Jukjeon-ro, Suji-gu, Yongin, Gyeonggi 448-701, Republic of Korea;1. CEA Marcoule, DEN, DTCD, SECM, BP 17171, 30207 Bagnols-sur-Cèze cedex, France;2. NIMBE, CNRS, CEA, Université Paris Saclay, CEA Saclay, 91191 Gif-sur-Yvette cedex, France;3. Institut Lumière Matière, UMR 5306, Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne cedex, France |
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| Abstract: | The eligibility of laser cleaning is tested on regionally specific sculptural stones. Marlstone and sandstone represent the most common building, architectural and sculptural stones employed in the Czech Republic since the Romanesque period. These stone types differ greatly from the marbles on which positive results have been obtained using laser cleaning. Experimental samples were prepared by sawing rock cores. Artificial blackening of samples’ surfaces simulates natural black patinas. The experimental laser cleaning was conducted using Nd:YAG commercial laser (Laserblast 50) at two different fluences—the low one corresponds to the minimum operating capability of the equipment, and the high fluence represents the maximum operating mode of the equipment (i.e. in the ordinary operating range of the equipment). The samples were cleaned under dry and wet conditions. Use of a high fluence resulted in cratering/spalling that is discussed in terms of rock mineralogical composition (presence of clay minerals), adsorption of moisture on clay minerals and physical properties (porosity). Tensional fracturing (evidenced by scanning electron microscopy) along the cleaned surface is the main mechanism of sample destruction due to the vaporization of adsorbed moisture and due to the different elasticity of present rock-forming minerals. Observed discoloration due to high fluence and insufficient cleaning effect of low fluence present other problems encountered. |
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