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This study deals with the analysis and characterisation of historic patinas on Spanish buildings from the sixteenth and seventeenth century by means of laser induced breakdown spectroscopy (LIBS). Indicative results from the analysis of these samples are shown. LIBS can be proven as an appropriate technique to characterise patinas and assist in a rapid and facile classification. The prospect of developing portable LIBS equipment makes the technique attractive for carrying out analyses on site.

Laser-induced breakdown spectroscopy (LIBS) was used to characterize the composition of black-and-white, silver-gelatine photographic films. LIB spectra of samples and reference gelatine (of various gel strengths, Bloom values 225 and 75 and crosslinking degrees) were acquired in vacuum by excitation at 266 nm. The elemental composition of the gelatine used in the upper protective layer and in the underlying emulsion is revealed by the stratigraphic analysis carried out by delivering successive pulses on the same spot of the sample. Silver (Ag) lines from the light-sensitive silver halide salts are accompanied by iron, lead and chrome lines. Fe and Pb are constituents of film developers and Cr is included in the hardening agent. The results demonstrate the analytical capacity of LIBS for study and classification of different gelatine types and the sensitivity of the technique to minor changes in gelatine composition. In addition LIBS analysis allows extracting important information on the chemicals used as developers and hardeners of archival cinematographic films.

In the present work, the feasibility of sulphur detection was demonstrated during laser ablation of the gypsum layers on the polluted surface of aged marbles. The laser used for cleaning and generation of the LIBS signal was a Q-Switched Nd:YAG emitting dual pulses at 1,064 nm. Different sulphur emission lines were identified through comparative LIBS measurements on gypsum encrustation and K2SO4 and MgSO4 reference materials, but only few, not weak, sulphur lines resulted suitable for monitoring the cleaning of marble, due to the overlap of most features with emissions from bulk marble constituents. Sulphur vertical distribution in the encrustation was then monitored by LIBS during the cleaning. Results of LIBS sulphur stratigraphy were comparable with those obtained by SEM–EDX measurements. In the present study it was possible to establish by LIBS the boundary between bulk marble and its encrustation containing gypsum and, consequently, to determine the optimal point for the interruption of the laser cleaning at the end of the heavily sulphated crust.

Based on a commercial miniature spectrometer, we have built a LIBSsystem for online monitoring and controlling during laser cleaning of artworks. In contrast to common LIBS set-ups with ICCDs, our system offers less sensitivity and λ-resolution. This system is unsuitable for high resolution elemental identification but it is applicable for the detection of “spectral fingerprints”. A powerful method of comparison online spectra during laser cleaning process with reference spectra is the analysis of correlation. Based on “Pearson’s correlation”, the linear relationship between entire data sets of both spectra are classified by the correlation coefficient r . In practise of laser cleaning a permanent comparison of the spectrum from the ablated layer with a reference spectrum of the layer to be preserved is necessary. Thus, online monitoring of the cleaning process is enabled by permanent estimation of r . In case of closed-loop laser cleaning the ablation will continue until r exceeds a predefined value and subsequently the ablation process is automatically stopped.

The Raman and laser-induced breakdown spectroscopy (LIBS) techniques were applied for the pigment identification in polychrome layers on a fourteenth/fifteenth century wooden crucifix. In the Raman spectra, characteristic bands associated with compounds of the pigment samples taken from different areas of the object are observed. Groups of bands corresponding to the original white, red, and green pigments allow the identification of chalk, vermilion, red lead, malachite, and azurite. From the presence of bands ascribed to Prussian blue (282, 538 cm ? 1) and chrome yellow (338, 360, 403 cm ? 1) known since eighteenth century, retouching of some statue parts can be concluded. The elemental composition is obtained from LIBS profiles recorded under excitation at 248 and 266 nm. The gold-leaf technique is identified and the presence of Cu, Pb, Cr, Fe, CN, C2, and Ca agrees with the pigment composition applied for re-touching and observed in the Raman bands.

During the last few years, the number of historical and archaeological items recorded using innovative, three dimensional surveying technologies has increased considerably. Comprehensive digital, photo-realistic 3D recording and modelling yields a huge range of new possibilities for documenting, analysing and safeguarding items of cultural importance. ArcTron GmbH has specialised in electronic surveying and the development of CAD and database information systems for heritage and archaeology for over 12 years employing total stations, laser pantographs and photogrammetry, as well as a variety of laser scanning systems, to generate 3D recordings. Innovative complementary combinations of these technologies allow their respective strengths to be fully exploited. The data resulting from recording techniques of these kinds can be used as a basis for producing documentation of outstanding quality. 3D digital models with photo-realistic texturing, orthophotos, coloured point clouds, 3D damage mapping, rapid prototyping models and multi-media presentations are just some of the potential resulting forms of documentation. Historical monuments and items ranging from huge sections of terrain down to the smallest artefact can be reproduced with such accuracy and to such a high level of realism that documentation of this kind is not only extremely useful for archaeologists, conservators and architectural historians etc. but practically indispensable.

With 47 samples of commercially available oil paints, the applicability of Optical coherence tomography to noninvasive tomography of paint layers was examined. Two different instruments, utilizing near-infrared light with central wavelength of 823nm and, for the first time, 1 . 55 μm, were used to obtain cross-sectional images. Example tomograms are given; a ray tracing correction of images is also discussed. The tests revealed that applicability of OCT is limited to certain pigments and the longer wavelength is better suited for this application.

With 47 samples of commercially available oil paints, the applicability of Optical coherence tomography to noninvasive tomography of paint layers was examined. Two different instruments, utilizing near-infrared light with central wavelength of 823nm and, for the first time, 155 μm, were used to obtain cross-sectional images. Example tomograms are given; a ray tracing correction of images is also discussed. The tests revealed that applicability of OCT is limited to certain pigments and the longer wavelength is better suited for this application.

The applicability of spectral optical coherence tomography (SOCT) for noninvasive and noncontact assessment of varnish layer thickness and structure on easel paintings is discussed. The SOCT tomograms of such objects are presented.

The changes of surface profile of oil paintings on canvas caused by rapid humidity are examined by spectral OCT. The speed, resolution, and long-time stability of SOCT make this technique appropriate for quantitative determination of surface profile changes.