Catálogo de publicaciones - libros

A low vacuum SEM was used to evaluate the effect of using an Nd:YAG laser as a non-contact technique for cleaning avian eggshells. The technique shows potential, since there are no obvious deleterious effects from cleaning, but further study is required to understand how the laser is interacting with the sample surface.

Mobile laboratory (MOLAB) is a unique joint collection of portable equipment for non-destructive in situ measurements. MOLAB activities are carried out within the frame of the Eu-ARTECH Integrated Infrastructure Initiative of the sixth F.P. In situ measurement is quite useful because it eliminates any risk connected to moving artworks or other precious objects to a laboratory. MOLAB instruments are accessible to European researchers through a peer-review selection of proposals. Starting from July 2004, MOLAB enabled non-destructive in situ studies of many precious artworks, such as paintings by Perugino, Raphael and Leonardo.

A parametric linear correlation method that enables the identification of the different elements in multicomponent LIBS spectra based on the comparison against reference spectra of individual elements is proposed. The method is described and preliminary tests are presented with spectral data obtained during the analysis of archaeological bronze.

Ancient leather samples from original upholstered furniture were treated with nanosecond Nd:YAG laser radiation with wavelengths of 1,064, 532, and 266 nm. The novel approach was the simultaneous application of these wavelengths. It opened new approaches for laser cleaning leather. Extensive diagnostics such as absorbance of different layers of leather, chemical composition and microscopic inspection studies before and after cleaning were conducted. Advantageous results with simultaneous UV–IR (266nm + 1,064nm) radiation are presented and discussed.

In order to find out whether the existing laser systems can be employed to remove superimposed layers of paint on secco wall paintings in a selective way, laser tests were carried out on three types of prepared samples simulating three stratigraphies that are frequently encountered in practice. OM, EPMA, colorimetry, μRaman, and FT-IR were used to evaluate the results. It was found that Q-switched Nd:YAG lasers emitting at 1,064nm could be employed to remove unwanted layers of oil paint and limewash, but the treatment of large areas requires implementation of a computer-controlled X–Y–Z station in order to control the parameters. However, the applicability of this technique will remain limited as ablation at the established optimum parameters implied a discoloration of the pigments cinnabar, yellow ochre, and burnt sienna. Moreover, it was observed that no ablation took place when the limewash thickness exceeds 25 μm. Unwanted layers of acrylic could be removed in an efficient way with an excimer laser emitting at 193 nm.

Drawings and photographs are often insufficient for documentation in the field of art conservation. A reliable documentation requires the acquisition of geometrical as well as colour information. For this purpose a mobile true colour topometric measurement system has been developed.

A documentation and analysing instrument with the name OptoTop ® was developed in order to measure the quality of laser cleaning on site and to document the individual stages of virgin surface area, reference area and the cleaned area on the building. The instrument comprises a fully automated optical documentation unit, which is portable and can be used without external power supply. Several high precision images of the area of interest are taken during the automated routine. A special newly developed software calculates first the 3D topography and also specific structure and macro- and micro-roughness parameters. As documentation for the visual impression of the human eye, an additional direct image of the area is taken and also analysed. This new instrument was applied in Austria, Spain, Ireland and Germany at several sites by several organisations and restoration companies. The results are shown and analysed. The benefits and limitations of this technology are demonstrated and discussed.

For numerous archaeological objects covered with strong sinter layers, restoration using traditional cleaning methods often fails. Within this study the potential of laser cleaning applied to archaeological pottery and glass artwork is presented. In this case the application of various Nd:YAG laser wavelengths leads to very satisfactory results, experimentally proven by SEM and EDX analyses.

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.

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.