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Laser-induced breakdown spectroscopy, or LIBS, has been used to characterize the elemental composition of the surface and interior of nineteenth-century, metal-based photographs called daguerreotypes. A surface plasma was produced by the infrared beam of a nanosecond Nd:YAG laser and the emitted light was dispersed in a monochromator to yield the spectroscopic identification of elements. Major components of the daguerreotype surface included silver, copper, and gold. The gold was only present on the surface, as evidenced by its absence after the first one or two laser shots. Minor components such as silicon, aluminum, calcium, and magnesium reflect contaminant particles arising primarily from the cover glass. Several “colored” or “tinted” daguerreotypes were analyzed and the pigments identified. Depth profiling, accomplished by monitoring the spectra as a function of multiple laser shots, allowed the thickness of the silver layer to be measured as the ablation laser “drilled” into the surface. The LIBS technique is shown to be useful in understanding the composition of daguerreotypes and for identifying the specific pigments used by the photographer. These data also provide a scientific basis for attempts to optimize laser cleaning of tarnished daguerreotypes and may also provide clues to the provenance of particular examples.

Laser irradiation may alter the colour of certain pigments used in artworks. Owing to the increasing use of lasers in artwork conservation, this problem becomes extremely crucial especially in the case of a polychromy covered by environmental encrustation. X-ray diffraction analysis and optical microscopy were used to study the crystalline structure of selected irradiated pigments in order to identify the changes that take place upon laser irradiation. Two representative pigments were studied, cinnabar (HgS) and lead white (Pb(OH)$_2$ 2PbCO$_3$). The results revealed a change in the crystalline phase or chemical composition, respectively, which can be barely detected owing to its superficial character, which is of a sub-micrometer scale.

Laser irradiation may alter the colour of certain pigments used in artworks. Owing to the increasing use of lasers in artwork conservation, this problem becomes extremely crucial especially in the case of a polychromy covered by environmental encrustation. X-ray diffraction analysis and optical microscopy were used to study the crystalline structure of selected irradiated pigments in order to identify the changes that take place upon laser irradiation. Two representative pigments were studied, cinnabar (HgS) and lead white (Pb(OH)22PbCO3). The results revealed a change in the crystalline phase or chemical composition, respectively, which can be barely detected owing to its superficial character, which is of a sub-micrometer scale.

Laser irradiation may alter the colour of certain pigments used in artwork. Owing to the increasing use of lasers in artwork conservation this problem becomes extremely crucial, especially in the case of a polychromy covered by environmental encrustation. X-ray diffraction analysis and optical microscopy were used to study the crystalline structure of selected irradiated pigments in order to identify the changes that take place upon laser irradiation. Two representative pigments were studied, cinnabar (HgS) and lead white (Pb(OH)2.2PbCO3). The results revealed a change in the crystalline phase or chemical composition, respectively, which can be barely detected owing to its superficial character, which is of a nanometre scale.

The application of laser-induced breakdown spectroscopy (LIBS) to monitor the laser cleaning process of polluted limestone from a historic building is examined. The combination of a Q-switched Nd: YAG pulsed laser with on-line diagnostics by the LIBS technique is shown to be very useful for controlling and characterizing the cleaning process in order to avoid overcleaning. In addition, the coupling of this spectroscopic technique to the cleaning process provides important information about the optimal experimental conditions to be selected for achieving an adequate cleaning procedure. Furthermore, the spectroscopic study of the plasma emission can be used to determine the elemental composition of both the black crust and the underlying stone. The application of LIBS as a diagnostic technique to monitor and control the laser cleaning process of limestone is based on the different elemental composition of the black encrustations covering the stone surface and the underlying stone. On the other hand, a different experimental setup for probing the ablation products by laser-induced fluorescence (LIF), in order to achieve a signal amplification of some atomic emission lines with weak intensity in the LIBS spectrum, is described.

The Excimer laser can be used to remove biological debris from underlying substrates. The ability of the krypton fluoride (KrF) Excimer laser to removeAspergillus nigermold, which had been grown on filter paper, was evaluated in the present study. The air in the immediate vicinity of the laser cleaning apparatus was sampled to determine if viable mold fragments were released into the air during treatment. It was found that filter paper could be sterilized with the Excimer laser wavelength with the proper selection of parameters. During this process, viable spores and mold fragments are released into the atmosphere, and pose a relative risk unless proper measures to prevent contamination of the work area are taken.

Pulsed ultraviolet laser ablation of two polyurethane films has been studied in terms of ablation rate behaviour and time-of-flight mass spectroscopy of the positively charged photofragments. Three excimer laser wavelengths (193, 248 and 308 nm; 17–30 ns pulse duration) and short-pulse laser system (pulse duration 500 fs or 5 ps, at 248 nm) were employed. The results of the influence of energy fluence on the ablation rate are tested against other photoablation models and a table of fitted physical constants is presented. The upper limit of the mean activation energy for desorption is found to be considerably lower than the energy required to break single covalent bonds. The mass analysis of the positively charged species produced during the photoablation process provides valuable insight into the photofragmentation mechanism.