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This chapter describes the surveying work and the creation of a 3D model of a Pegasus statue, which builds the basis for a static analysis. The supporting legs of the statue were surveyed with the close-range laser scanner, Minolta VIVID 900. Approximately 45 individual scans were required to cover each leg. The rest of the statue was surveyed with the terrestrial laser scanner, Riegl LMS-Z420i with eight individual scans. The surveying of the statue using these two laser scanners is particularly interesting because the statue represents a rather “small” object for a terrestrial laser scanner, whereas for a close-range laser scanner it represents a rather “huge” object. With the aid of photos of the statue, the relative orientation between the different laser data was determined in the course of a hybrid bundle block adjustment. Finally, a “waterproof” 3D model of this complex statue was derived.

Three different undyed, unweighed silk fabrics (new clean, new soiled, and naturally aged) were cleaned with a computer-controlled Q-switched Nd:YAG laser at 532nm in 30 combinations of fluence and pulse numbers. They were studied for chemical change by viscometry, X-ray diffraction, and FIB-SIMS in combination with temperature calculations. While physical changes only occurred above the tested parameters, chemical changes could be detected as low as 0 . 2 J cm ? 2 with four pulses. Yellowing was observed at lower and bleaching at higher fluence/pulse number combinations. Melting was observed in naturally aged silk cleaned with 64 pulses at 4 . 2 J cm ? 2. The temperature reached at 0 . 1 J cm ? 2 is sufficient to evaporate carbon. Excess energy is transferred into the silk substrate causing thermal degradation. Different chemical processes leading to chain scission and to crosslinking seem to occur simultaneously, even at low fluence and pulse number. An increase in pulse numbers also leads to increasing damage.

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 Santa Tecla of Cervera de la Cañada , Zaragoza , fifteenth century, and appliqué relief brocades on wooden sculptures of the Chapel of San Miguel , Cathedral of Jaca , Huesca , sixteenth century.

The conservation of mural paintings requires a deep knowledge of the alterations caused by natural ageing, environmental agents and previous restoration treatments. All the operations concerning cleaning and consolidation of wall paintings must assure the safety of the paint layers. This is especially true the more fragile the painting technique. For example, “ a secco ” paintings, executed with organic binders such as tempera, oil, glue, when altered and damaged, present a very weak adhesion to the mortar underneath, and provoke detachment of paint fragments. In this circumstance it is necessary to find a feasible alternative to the usual cleaning methods (wet and mechanical ones) and a valid way to operate. Moreover, the removal of scialbo layers (a thick, pure lime layer applied on the wall painting) presents difficulties in order to preserve the integrity of the painting layers. Previous experiments carried out in Opificio with Er:YAG laser on easel painting cleaning, lead us to extend the experiments on the cleaning of mural paintings.

In practical restoration – depending on the object in question and the regional attitude to monument restoration – widely differing techniques and restoration philosophies have been, and still are, applied to the exposure of metal. Depending on the type of metal, this results in differing working materials as well as highly diverging definitions of the required degree of exposure as far as removing corrosive deposits is concerned. Therefore, particularly where metallic or heat sensitive cultural assets are concerned, the applicability of an efficient cleaning procedure using contact-free laser beam technology, which is also gentle on the material, should be examined.

This chapter deals with the cleaning of the Parthenon West Frieze by means of an innovative laser cleaning methodology. Following a comparative study of various cleaning methods, laser cleaning was proven to be the most efficient method for the removal of loose deposits and black crusts. The laser system employed is a Q-switched Nd:YAG system emitting at the fundamental and the third harmonic frequencies designed and developed by FORTH-IESL. The system emits in two wavelength beams individually or in combination. This feature, along with possible modification of the laser parameters – energy density, number of pulses, the contribution of each beam to the final combined beam – for each individual case of encrustation and substrate (marble, monochromatic layers), leads to a safe and controlled cleaning result. The project commenced in 2002 and was completed in January 2005. Since then, the Parthenon West Frieze is on display at the Acropolis Museum in Athens, Greece.

In Steyr, Austria, a Renaissance epitaph was cleaned by an Nd:YAG laser. Compared to cleaning tests, carried out with microsandblasting, (NH4)2CO3 and water compresses, the laser cleaning was much more sensible and faster. Satisfying results were realized for the calcareous sandstone of the frame as well as for the red and compact limestone of the relief. One of the big advantages was the detection of several traces of pigments, which were observed during the layered cleaning process. It can be assumed that other cleaning methods could not hold these last spots of polychrome surfaces. Care had to be taken of the energy. The application of higher energies on the red marble leads to colour changes into yellowish red.

Roman ceramics Terra Sigillata from different production areas have been analyzed by means of “laser induced plasma spectroscopy” (LIPS). The overall objective of this study is to show the capability of LIPS to classify these archaeological ceramics as a function of their provenance. The use of linear correlation methods allows us to cluster the samples by quantitative comparison of their LIP spectra, leading to a reliable assignment of Terra Sigillata pieces to their regions of origin and establishing reference groups for the purpose of assigning future pieces.

The aim of this investigation and conservation study was to examine and evaluate the laser ablation method as a practical technique for cleaning of Indiana limestone, a calcite-cemented stone widely used in historic structures throughout the United States. To this goal, a thorough petrographic characterization of the samples was performed prior to and following laser cleaning tests by Q-switched and short free running Nd:YAG lasers. The main optimization problem was the amber-gray appearance associated with the laser ablation by Q-switching lasers. Following the evaluation of such a cleaning result, two practicable solutions based on suitable pulse duration or wavelength selections were successfully demonstrated and then compared with different intervention protocols proposed. This chapter will show that through this case study, an understanding of effective uses of cleaning highly weathered Indiana limestone through the use of three types of Q-switched and short free running Nd:YAG lasers can be most effective in the removal from limestone of surface soiling and thick built-up carbon deposits ranging from 0.5 to 1mm in thickness. Case study evaluation methods included petrographic examination of composition, texture, and microstructure using optical microscopy and scanning electron microscopy performed on thin and polished sections of limestone sampled from six areas before and after cleaning. The microscopy studies were supplemented with energy-dispersive X-ray spectroscopy to characterize crystalline phases and track changes in chemistry.

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.