Catálogo de publicaciones - libros

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.

This work presents the results of laboratory tests aiming at the characterization of painting materials by LIB and FT-Raman spectroscopies and at identification of the best laser cleaning conditions of polychromes of Spanish Heritage: polychromes on gypsum mortar of the Church-Fortress of of , , fifteenth century, and appliqué relief brocades on wooden sculptures of the Chapel of , Cathedral of , , sixteenth century.

We report the results of a successful experimentation of the laser cleaning technique on wall paintings using intermediate pulse duration Nd:YAG lasers at the fundamental wavelength (1,064 nm).

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.

Traditional paper cleaning techniques are not always sufficient for cleaning artefacts. The pulsed laser cleaning can offer a valuable tool for solving problematic cases in paper conservation. Comparative studies of traditional and laser cleaning were performed on historic picture post cards. The results demonstrate the possibilities of partial laser cleaning using nanosecond laser pulses at a wavelength of 532 nm.

The laser cleaning of painted artefacts relies on the synergy of thermal, photochemical and photomechanical effects, which are involved in laser ablation. A crucial issue, however, for a successful cleaning intervention is the spatial confinement and control of these effects for safeguarding the original surface from potential damage. Extensive studies have shown that in many cases there is an optimum interplay of laser and material parameters, which resulted in successful laser cleaning applications. The laser pulse duration is an important parameter in this context.

In this study, tests were undertaken to ascertain whether the laser could achieve a better level of cleaning on polyurethane foam than vacuum cleaning. Optimum laser parameters were found using statistics on data from color measurements. The laser proved to be very effective regarding the removal of dust, but also caused damage on some PU-variants. The laser cleaning has been carried out at National Workshops for Arts and Crafts, Copenhagen, Denmark.

In this work a series of egg tempera paint and varnish systems have been prepared, artificially aged and irradiated with KrF excimer laser at a wavelength of 248 nm. The samples were prepared with pure pigments and selected mixtures. It was found that, for some pigments, the colour changed upon laser irradiation even at low energy densities, below the ablation threshold while for other inorganic pigmented egg temperas the degree of discoloration is very small at moderate fluence of 0.30 J cm2. The varnish systems did not present signs of discoloration. The thickness, superficial roughness and magnitude of the colour changes of the samples were measured. X-ray diffraction, Raman spectroscopy and UV/visible spectroscopy were used in order to investigate the changes induced by the KrF excimer laser radiation.

Nanosecond laser (532 nm) cleaning of soiled silk (naturally aged and new fabrics) is discussed in terms of an adequate choice of the processing parameters laser fluence and pulse number to achieve a satisfying cleaning effect and to avoid damage of the sensitive textiles. Experimental limits will be presented and compared to theoretical considerations utilizing graphite as a model for the soil.

Art Conservation B.V. participates in the PaReLa project, a European Commission funded, cooperative research project entitled ‘Paper Restoration using Laser Technology’ (EVK4-CT-2000-30002). The purpose of this project is to develop a laser system suitable for the accurate, efficient and safe cleaning of paper objects. Other participants include BYB, Guillet, Hai Yen, Susan Corr, TNO, BAM, ICN and FORTH. Our paper discusses the research outcomes and the feasibility of this method in practice. For research purposes we aged a great number of samples, plastered with different types of tape, in special ovens. Next we carried out experiments using various types and doses of laser light to determine how the adhesive residues can best be removed. It appears that the laser system can yield excellent results.