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Laser technology in art conservation
Abstract and Figures
Applications of modern laser technology in art conservation are reviewed with emphasis in the conservation of painted artworks. In particular, processes and critical parameters for the cleaning of paintings by excimer lasers are discussed. The influence of photoxidation or free radical formation processes leading to potential damage is examined in experiments involving model and realistic systems. Laser based spectroscopic techniques for non-destructive pigment and media analysis are also presented. A particular issue in this respect is the applicability of such techniques for on-line control of the cleaning process safeguarding from any damage. © 1997 American Institute of Physics.
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... Research on the specific procedure of laser varnish removal began with ns excimer lasers operating in the ultraviolet (UV) range (mainly ArF 193 nm and KrF 248 nm) [1][2][3][4][5][6]. The choice of this wavelength range was motivated by the high absorption of most natural varnishes within it, guaranteeing the possibility of a laser ablation process [1]. ...
Varnish removal from easel paintings is a restoration procedure that is regularly undertaken by cultural heritage conservators. In very few cases, traditional methods (chemical and mechanical) do not allow them to reach the goal of a perfectly controlled and selective cleaning. UV laser ablation has been considered since the 1990s to overcome these limitations, but its application to real cases is far from common practice. This study proposes a calibrated procedure based on ablation by an ns UV Nd:YAG laser at 266 nm combined with optical coherence tomography for micrometric laser varnish removal from inhomogeneous and highly photosensitive pictorial layers. The use of this wavelength for varnish removal, not adapted according to the literature, is discussed again after the beam shaping leading to a homogeneous and controlled intensity distribution. The innocuity is controlled by laser-induced luminescence, and some solutions for the transparency loss of the residual varnish following ablation are proposed.
... Similar LIBS studies which have appeared previously in the literature have used ratios of spectral lines [13] and calibration curves [15] in order to differentiate between different plastics. In more detail, in the former study, LIBS has been applied on some plastic/polymer samples, namely high-and low-density polyethylene (HDPE and LDPE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polypropylene (PP). ...
In the present work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for the discrimination/identification of different plastic/polymeric samples having the same polymeric matrix but containing different additives (as e.g., fillers, flame retardants, etc.). For the classification of the different plastic samples, some machine learning algorithms were employed for the analysis of the LIBS spectroscopic data, such as the Principal Component Analysis (PCA) and the Linear Discriminant Analysis (LDA). The combination of LIBS technique with these machine learning algorithmic approaches, in particular the latter, provided excellent classification results, achieving identification accuracies as high as 100%. It seems that machine learning paves the way towards the application of LIBS technique for identification/discrimination issues of plastics and polymers and eventually of other classes of organic materials. Machine learning assisted LIBS can be a simple to use, efficient and powerful tool for sorting and recycling purposes.
... The respect of the artwork, its state of conservation and the preservation of the historicalenvironmental context are at the centre of the modern concept of restoration. To this aim, the laser-based techniques are largely and successfully used in the field of cultural heritage for diagnostic applications 1 . The characterization of the surface composition of artworks is important for several reasons, including the determination of its preservation status, the study of the cleaning procedures effects, and also to gain information on past and not well documented restoration steps. ...
... Lasers can be employed to efficiently and precisely remove contaminated layers and unwanted particles from a great variety of surfaces [1][2][3] and in some cases even are the only cleaning device available for this task. Engineers and laser specialists at the FO.R.T.H (Foundation for Research and Technology Hellas) in Greece have been highly successful in exploiting an excimer laser in a prototype system for selectively ablating aged varnish, fungi or over-paint layers from old paintings [4][5][6][7][8][9][10][11], as well as black crust from marble/stone [12,13]. An on-line LIBS-system (Laser Induced Breakdown Spectroscopy) ensures the proper ablation depth is reached. ...
In the present work, a cleaning method using a KrF-laser for selective, non-contact removal of various layers from paintings will be described. The focus of this paper lies on the up-gradation of the present experimental system at FO.R.T.H. to a professional cleaning station for treatment of larger artworks. In the present work, an outline of the selected scanning movement, accuracy and design of the professional laser station is introduced. Finally, various aspects of the control and operation are addressed.
... A number of laser material processing and spectroscopic techniques have been adapted to the special requirements of a variety of conservation applications [1][2][3][4]. Laser cleaning and diagnostic of artworks and antiquities, relying on the use of different types of lasers, have proven successful in many cases [2,4]. Laser based diagnostic techniques are largely non-intrusive and appropriate for the in situ analysis of composition and structural diagnosis of objects. ...
Wood is one of the most valuable and abundant renewable materials. Development of wood-based advanced products comprises an important and exciting area of research. In recent times, replacement of traditional technology for the improvement of wood preservation and drying has drawn substantial scientific interest. These technologies are important for improving the functional properties of wood. More accurate and rapid determination of wood properties adds value to the appropriate utilization of wood and its aesthetic value, which plays a significant role in the market. In this regard, lasers are a promising technology in wood science for architectural essence and furniture making to toys and fine crafts. Utilizing this technology ranges from simple incision to development of advanced wood-based products and ensured environmental sustainability. Better elucidation of the working principle and optimisation of lasers in wood science promotes opportunities for the development of industrial wood-based products. This review, critically presents various laser applications that improve wood functionality and have the potential to enhance sustainability of wood-based products and industries.
The heat generated during the welding of stainless steel results in the oxidation of the surface that, apart from aesthetics, adversely affects its corrosion property too. This communication reports the successful removal of heat tint generated by the gas tungsten arc welding process off a stainless steel surface in addition to an improvement in its pitting corrosion resistance by exposure to the emission of a nanosecond pulsed fiber laser. The laser cleaning experiments, conducted with six different laser pulses having different temporal shapes and duration that varied from 20 to 1020 ns, revealed that removal of the weld heat tint was possible in all conditions provided the effective laser fluence exceeded a definite threshold value. This threshold value, in turn, was found to increase with an increase in pulse duration. The laser cleaned specimens were subsequently analyzed for surface morphology, roughness, and pitting corrosion resistance. The pitting corrosion resistance of the laser-treated specimens was compared with the as-welded specimens and welded specimens with heat tint removed using conventional methods like wire brush cleaning and chemical pickling. The superior quality of tint removal, improved pitting corrosion resistance, and the ease of noncontact operation indicates the significant potential of the fiber laser-based weld tint removal method to substitute the conventional mechanical or chemical cleaning methods currently in use in the manufacturing industry.
This work explores the control of ultrafast laser ablation plume composition and kinetics by temporal shaping of femtosecond laser pulses. The goal is the optimization of thin films and nanoparticles deposition. Chapter 1 is a synthesis of the literature on femtosecond laser deposition of thin films. The focus is on Diamond-Like Carbon films and nanoparticles. The impact of laser temporal pulse shaping on the ablation mechanisms is developed. Ablation plume diagnostic methods are detailed. Chapter 2 describes the experimental setup for temporal pulse shaping and plasma diagnostic. The latter is done through space and time-resolved optical emission spectroscopy and extinction spectroscopy. Chapter 3 reports on the impact of doubles pulses and long pulses on aluminium and boron ablation plumes. Ion yield enhancement in aluminium ablation plasma is explained through hydrodynamics simulations. In chapter 4, various temporal pulse shapes are used for graphite ablation and Diamond-Like Carbon thin films deposition. The control of the plume kinetics is reached by selectively populating the various plume speed components: molecules, atoms, ions. Even though the deposited Diamond-Like Carbon structure is unaffected, it has been observed an improvement of the thin films surface. Chapter 5 shows the efficiency and sensitivity of optical extinction spectroscopy for in situ measurement of nanoparticles size distribution in femtosecond laser ablation plumes
The use of excimer laser ablation for the restoration of painted artworks is reviewed with emphasis on the plausible short- and long-term effects of the procedure on the state of the paintings. The dependence of the efficiency of the process and of the surface morphology on laser parameters is discussed. The importance of photochemical effects is addressed by chromatographic analysis of irradiated realistic samples for the detection of photoproducts. It is shown that varnish plays a critical role for the success of the technique. The importance of varnish is further examined in experiments on model samples with photosensitive dopants incorporated. Factors responsible for the "protecting" role of the varnish are proposed. Finally, the potential consequences of laser-induced photomechanical effects are addressed via the use of holographic interferometry. In all, these experiments indicate that optimal fluence ranges can be defined for a highly selective and effective cleaning with minimal or insignificant damaging effects to the substrate.
Laser Induced Breakdown Spectroscopy (LIBS) has been applied to inked linen textile that belongs to a mummy's linen wrapping dated back to the Ptolemaic period (330 BC: 30 AD). The rarity of the ancient archeological piece introduced in this study has suggested the use of a model sample of currently manufactured linen for comparison purposes and optimization of the experimental conditions. The Nd:YAG laser operating at both wavelengths 532 and 1064 nm as our excitation source along with an Echelle spectrometer with an intensified charge-coupled device detector has been employed. Under the experimental conditions adopted throughout this work, the use of the visible 532 nm laser produced poorer S/B when compared to that produced by a 1064 nm laser which suggests the production of colder plasma leading to less atomization of the ablated material. Additionally, the 532 nm wavelength shows a negative behavior in ablating ink writings which was visually clear. Although, LIBS qualitative results are so comparable to that of SEM-EDX, some elements were detected only by LIBS which could be attributed to the irregularity of ink on linen. Thus, the capabilities of LIBS should be extensively exploited to the in situ measurements and analysis of archeological ink and fabrics.
The precise and controlled cleaning of polluted limestone sculpture by a Q-switched Nd:YAG laser is described. Acoustic monitoring of the cleaning process is used to demonstrate the selective removal of black crusts from stone surfaces. Results are also presented which show that by applying a thin layer of water to the surface of the crust prior to irradiation, cleaning can be achieved at a lower energy than with normal laser cleaning. The probability of damage to the underlying stone is, therefore, reduced.
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