Results of the recent application studies of laser-based techniques for conservation practice, carried out in the frames of
research and conservation projects are presented and discussed. The Gotland Sandstone Project covers laser cleaning,
spectroscopic techniques of the process monitoring and materials analysis. The post-processing effect is investigated by
means of LIBS, colorimetry, SEM and XEDS in order to answer questions regarding encrustation removal, discoloration
and alteration due to environmental pollution and laser interaction, respectively. The cleaning is monitored acoustically.
Slight differences in stone yellowing are revealed when applying laser in air or pure N<sub>2</sub> environment which is ascribed to
material oxidation and partial combustion of surface remnants due to presence of O<sub>2</sub> contributing to the final effect of
laser cleaning. Results of microscopic observation are supported by the presence of elements S, Al, Ca, and C which
prevail in crust. In case of restoration of the historical documents on paper the ablative cleaning and the nearly nondestructive
identification and composition analysis of surface layers such as contaminants, substrate and pigments are
performed. Spectra obtained by means of the LIPS technique for historical, originally contaminated and also artificially
soiled model samples reveal reach structures. The emission lines of Ca, Na, K, Al and Fe are ascribed to contaminants
because of intensities decreasing with prolonged surface irradiation during laser cleaning. Bands of Ti and Ba correspond
to white pigments (TiO<sub>2</sub> and BaSO<sub>4</sub>) in the paper and are confirmed by the Raman spectra as well. For identification of
historical pigments the reference measurements on model substrates are performed, too.
Techniques of laser emission spectroscopy such as LIPS and LIF are applied to identify pastels and pigments composition for the use in conservation of historical documents. The question of data reliable for pigment identification by these techniques is considered. For model samples made of the cotton paper of chemical composition corresponding to the historical ones, and coated with pastels of different colors the LIPS and LIF spectra are recorded. Samples are excited by the pulsed Nd:YAG laser operating at 355 or 266 nm. The reference Raman spectra are collected, too. Bands characteristic for the blue pigments: PB15, PB29; violet one PV16, and yellow PY 184 are identified exclusively by LIPS in agreement with literature. Also additives such as the barium white found in the Scarlet pastel, and ultramarine (Na<sub>8-10</sub>[Al<sub>6</sub>Si<sub>6</sub>O<sub>24</sub>]S<sub>2-4</sub>) with titanium white (TiO<sub>2</sub>) in the Phthalo Blue are identified, and confirmed by the Raman technique as well. The pigments anthraquinone (PR 168), isoindolinone (PY 110) and monoazo (PY 74) are not revealed. In the LIF spectra only a broad band centered at 612 nm and corresponding to anthraquinone (red pastel) can be clearly assigned.