title: Wavelength and pulse duration effects on laser induced changes on raw pigments used in paintings.
abstract: In this study, the reaction of widely used artist's pigments in raw form to pulsed laser radiation of different wavelengths and pulse duration was investigated. Vermilion, lead chromate and malachite (in the form of pellets) were irradiated using laser pulses of 500 fs at 248 nm, and pulses of 150 ps and 15 ns at 1064 and 213 nm. Optical microscopy, colorimetry, spectrofluorimetry, micro-Raman spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the physicochemical changes induced to the pigments. Change of crystalline phase was identified for vermilion while reduction processes take place for lead chromate and malachite. It was found that these effects were minimized by application of ultraviolet ultrashort pulses (of femtosecond and picosecond duration) as compared with changes occurring by pulsed infrared irradiation (of both picosecond and nanosecond duration). The results presented are discussed in relation to previous research on painted mock-ups in order to elucidate the role and significance of the binding media in the laser induced discoloration of painted surfaces and thus to propose optimum laser cleaning practices.
authors.affiliation: Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain. m.oujja@iqfr.csic.es
authors.forename: M
authors.initials: M
authors.lastname: Oujja
authors.forename: M
authors.initials: M
authors.lastname: Sanz
authors.forename: E
authors.initials: E
authors.lastname: Rebollar
authors.forename: J F
authors.initials: JF
authors.lastname: Marco
authors.forename: C
authors.initials: C
authors.lastname: Domingo
authors.forename: P
authors.initials: P
authors.lastname: Pouli
authors.forename: S
authors.initials: S
authors.lastname: Kogou
authors.forename: C
authors.initials: C
authors.lastname: Fotakis
authors.forename: M
authors.initials: M
authors.lastname: Castillejo
mesh_terms: D002840:Chromates / Q000737:chemistry; D003124:Colorimetry; D004396:Coloring Agents / Q000737:chemistry*; D003460:Crystallization; D007834:Lasers; D007854:Lead / Q000737:chemistry; D008853:Microscopy; D009942:Organometallic Compounds / Q000737:chemistry; D010151:Paintings; D056951:Photoelectron Spectroscopy; D013059:Spectrum Analysis, Raman
chemical_list: D002840:Chromates; D004396:Coloring Agents; D009942:Organometallic Compounds; C520661:malachite; D007854:Lead; C031895:lead chromate