Laser cleaning of 19th century Congo rattan mats

• Published in: Applied surface science 2011-09, Vol.257 (23), p.9935-9940
• Main Authors: Carmona, N., Oujja, M., Roemich, H., Castillejo, M.
• Format: Article
• Language: English
• Subjects: Cleaning; Collection; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conservation; Cross-disciplinary physics: materials science; rheology; Damage; Exact sciences and technology; Irradiation; Laser cleaning; Lasers; Mats; Museum objects; Physics; Rattan; Scanning electron microscopy; UV–vis spectroscopy; Wavelengths
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.06.111

• In this study we present a laser cleaning approach for the restoration of 19th century rattan mats. • We found an efficient removal of the dark carbonaceous soiling while maintaining the original substrate with the second harmonic of a Q-switched Nd:YAG laser. Safe fluence range was defined between 0.4 and 0.6Jcm−2. • Additional SEM and UV–vis spectroscopy helped to the observation of irradiated surfaces. • Preliminary laboratory tests and optimization of all parameters involved are essential for the best laser cleaning of cultural heritage objects. There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical cleaning may be too abrasive for sensitive fibers. In this work we present a successful laser cleaning approach for 19th century rattan mats from the Brooklyn Museum collection of African Art, now part of the study collection at the Conservation Center in New York. Tests were carried out using the fundamental (1064nm) and second harmonic (532nm) wavelength of a Q-switched Nd:YAG laser to measure threshold values both for surface damage and color changes for different types of rattan samples. The irradiated substrates were investigated by optical microscopy, scanning electron microscopy and by UV–vis spectroscopy in order to determine the efficiency of laser cleaning and to assess possible deterioration effects that may have occurred as a result of laser irradiation. The study showed that by using the laser emission at 532nm, a wavelength for which photon energy is below the bond dissociation level of the main cellulosic compounds and the water absorption is negligible, it is possible to select a range of laser fluences to remove the black dust layer without damaging the rattan material.