Analysis of ceramics surface modification induced by pulsed laser treatment (original) (raw)
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Studies of the Iranian medieval ceramics surface modified by pulsed tea CO2 and Nd:YAG lasers
Ceramics International, 2015
This paper presents the results of the morphological and chemical changes on the surface of an Iranian ceramics sample irradiated by a Transversely Excited Atmospheric (TEA) CO 2 and an Nd:YAG laser. The sample originates from the archeological site of Yazd (Iran) and is assumed to have been a part of an aqueduct. The effect of laser parameters (energy density (fluency), number of pulses and wavelength) on the induced changes was studied. The tests were performed in order to establish the mechanism of the interaction with the fluence above the damage threshold. This is an essential parameter in the use of lasers for cleaning as well as for eliminating surface defects such as cracks, by melting superficial layers and thus strengthening the objects in question. Another objective was to obtain as much as possible information about the material composition necessary for the conservation and restoration of this ceramics. A TEA CO 2 (10.6 μm wavelength, pulse duration 100 ns (Full Width at Half Maximum-FWHM)) laser and an Nd:YAG laser (wavelength 1064 nm and 532 nm, FWHM ¼ 150 ps) have been used for the surface treatment. Laser fluences were in the range of 1-20 J/cm 2. The ceramics surface morphology modifications, induced by pulsed lasers, were characterized by a scanning electron microscope (SEM), while the composition was examined by energy-dispersive (EDX) and X-ray fluorescence (XRF) spectroscopy. The results show that there are significant differences depending on the laser applied and whether the surface is glazed or not.
Laser restoration of ceramic artifacts with archeological value
11th International School on Quantum Electronics: Laser Physics and Applications, 2001
A new method for restoration of ceramic surfaces, based on laser ablation of iinpunties has been developed. Optical pulses generated by Nd:YAG laser are used to remove a high absorbing layer (fungi) from the surface of a lower absorbing ceramic substrate. Two regimes of operation have been employed: Q-switched mode and free nrnning mode. Analysis suggests that Q-switched mode of operation is the most efficient for cleaning processes. Densities of energy 1.60 -1.90 J/crn2 at the fundamental wave and pulse duration 10 ns are the typical values for removing of impurities of fungi from ceramic surfaces. The second, third and forth harmonics of the Nd:YAG laser have been also used for optimization of the process oflaser restoration. The absence of structural changes of the ceramics surface after the process of laser cleaning has been observed by X-ray analysis. The used ceramic substrate is dated 5000 BC-a part ofthe excavations near Durankulak.
Laser restoration of ceramic artifacts with archeological value
2001
A new method for restoration of ceramic surfaces, based on laser ablation of impurities has been developed. Optical pulses generated by Nd:YAG laser are used to remove a high absorbing layer (fungi) from the surface of a lower absorbing ceramic substrate. Two regimes of operation have been employed: Q-switched mode and free running mode. Analysis suggests that Q-switched mode of
Study of the laser cleaning on plaster sculptures. The effect of laser irradiation on the surfaces
Optics and Spectroscopy, 2013
The focus of this paper is to study the effects caused by the laser irradiation on nineteenth and twentieth century plaster sculptures. Before applying the laser cleaning on the sculptures, it was tested on samples prepared in laboratory according to the results of the scientific investigation carried out on the selected works of art. The characterization of the surface finishing materials of the sculptures was performed by Fourier Transform Infrared spectrometry (FTIR), X ray Fluorescence spectroscopy (XRF), UV fluores cence photography, and internal micro stratigraphic analysis. Regarding the finishing materials, shellac, zinc white, siccative oil and proteins were found on the surfaces. The results of the scientific investigation, together with the examination of the ancient technical manuals, were used to create the laboratory samples to carry out the irradiation tests with laser. The laser irradiation and cleaning tests were carried out with a Q switched Nd:YAG system. The irradiated surfaces were analyzed before and after the laser tests with the aid of a video microscope and a reflectance spectrophotometer, in order to evaluate the color changes of the surfaces. The possible morphological modifications caused by laser irradiation were also investigated by Scanning Electron Microscopy (SEM) together with ancillary Energy Dispersive Spectroscopy (EDS) elemental analysis. Con cerning the laser cleaning test on the samples, in general little color changes were observed both with the 532 and 1064 nm wavelength. Total color changes, expressed as ΔE*, are always small apart from the samples made of shellac and zinc white in linseed oil, as finishing layer. As regards these samples the surface irradiated with the laser greyed lightly, corresponding to a decrease of L* parameter (lightness). SEM imaging of the treated and not treated samples, both at low and high magnification, does not show evidence of significant morphological differences due to the laser beam irradiation. Starting from these results, some laser cleaning tests were carried out on the original sculptures, putting them in comparison with an aqueous cleaning method. It was found that the laser cleaning removes effectively the dirt layer preserving the original finishing on the sculpures' surface, whereas the aqueous cleaning system removes also the finishing.
Using lasers for cleaning ceramic and plaster patrimonial objects
… : Optics for the …, 2003
Traditional cleaning techniques (sandblasting, chemical, ... ) turn out to be ineffective or damaging on some ceramics and plaster objects. It's especially true on outdoor ceraIJÙCScovered with black crust or indoor biscuits wares and plasters exposed to dust and repeated handling. The use of lasers to remove dirt, such as for stone, has then been considered. This paper study the behaviour of these materials under the impact of different type of lasers irradiation (Nd:YAG first and third harmonic, excimer, ... ). According to the type of dirt and underlying material, the effectiveness of cleaning depends on the laser wavelength and its energy density. The results are satisfactory with no damage and no coloration change on plaster cleaning by Nd: yAG third harmonic.
Laser cleaning in art restoration
Applied Surface Science, 1996
Preliminary results of the application of a Nd:YAG pulsed laser in the cleaning of limestone from a historic building are presented. Evaluation of the effect of laser irradiation on surface morphology was carried out using optical microscopy and scanning electron microscopy (SEMI. Under optimized experimental conditions, no significant changes in me chemical and mineralogical composition of the underlying stone were detected by means of micro Raman spectroscopy, SEM and energy dispersive X-ray analysis (EDX). 0169-4332/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDl 0169-4332(95)00461-O
Laser Cleaning of Archaeological Bronze Artefacts
2016
The study is devoted to the development of tailored laser cleaning procedures for the selective removal of dangerous corrosion products on archaeological bronze artefacts, without affecting the metallic substrate. In order to optimise the cleaning methodology and assess the real feasibility of the laser treatments as conservation procedure for metallic works of art, a deeper knowledge of the laser-material interaction and an investigation of the effect of the different experimental parameters on the metallic surface are necessary. In this study, a set of artificially-patinated Cu-based reference samples were cleaned by using a near-IR Q-switched Yb:YAG fibre laser. Several laser parameters (e.g. pulse duration and output laser power) were considered. The artificial patinas and the cleaned samples were characterised from the chemical, microstructural and morphological point of view by means of X-Ray micro-diffraction, scanning electron microscopy and confocal microscopy in order to a...
Tests of laser cleaning on archeological metal artefacts
Journal of Cultural Heritage, 2000
Previously reported experiences on laser cleaning of metal surfaces of artworks such as statues and decorations altered by atmospheric pollution demonstrated the potential advantages of this technique. Here we present a study on the use of laser cleaning on excavated metal objects that typically show alterations and corrosion processes quite different with respect to exposed metal artefacts. Tests were performed on a selection of archaeological samples, such as coins, plates, clamps and ornaments collected from Italian sites. Metals considered in this study are bronze, copper, silver and lead. Different laser systems and different irradiation conditions were employed and compared. The results, evaluated by metallurgic diagnostics and objective observations, indicated that the laser cleaning process was selective and highly precise, allowing the preservation of fine surface details. © 2000 É ditions scientifiques et médicales Elsevier SAS
Laser cleaning experiences on sculptures’ materials: terracotta, plaster, wood, and wax
Fundamentals of Laser-Assisted Micro- and Nanotechnologies 2013, 2013
The focus of this paper is to show the work experiences with laser cleaning on sculptures made of terracotta, plaster, wood and wax. These materials exhibit peculiar features that often prevent the use of traditional cleaning procedures to remove the surface dirt, soot or carbonaceous deposits and other materials coming from environment or ancient conservative interventions. To overcome the difficulties in the cleaning of the above mentioned materials, laser technology was tested. The laser irradiation and cleaning tests were carried out with a Q-switched Nd:YAG system under the following conditions: wavelength 1064 nm and 532 nm; energy 4-28 mJ; pulse duration 10 ns; spot diameter 2-8 mm; frequency 5 Hz. The irradiated surfaces were analyzed before and after the laser tests, with the aid of a video microscope and a reflectance spectrophotometer, in order to evaluate the morphology and colour changes of the surfaces. Before starting with the cleaning intervention, some diagnostic analysis was performed on the sculptures in order to obtain the identification of the original materials and of the surface deposits. Concerning this, Fourier Transform Infrared spectroscopy, X-ray fluorescence spectroscopy, and internal micro stratigraphic analysis were performed. This research demonstrated that the laser cleaning is an effective method to remove the surface deposits preserving the original patina of the sculptures and the opacity of the wax. The results gathered in this work encourage to continue the research in order to better understand the interactions between the laser beam and the surfaces and to find the most appropriate laser conditions to clean the sculptures.
Applied Physics A, 2012
In the present work the application of laser cleaning in the conservation of cultural assets is reviewed and some further developments on the interpretation of the associated laser-material interaction regimes are reported. Both the state of the art and new insights mainly focus on systematic approaches addressed to the solution of representative cleaning problems, including stone and metal artifacts along with wall and easel paintings. The innovative part is entirely dedicated to the extension of the application perspective of the Nd:YAG lasers by exploiting the significant versatility provided by their different pulse durations. Besides extensively discussing the specific conservation and physical problems involved in stone and metal cleaning, a significant effort was also made to explore the application potential for wall and easel paintings. The study of the latter was confined to preliminary irradiation tests carried out on prepared samples. We characterized the ablation phenomenology, optical properties, and photomechanical generation associated with the irradiation of optically absorbing varnishes using pulse durations of 10 and 120 ns. Further results concern the nature of the well-known problem of the yellowish appearance in stone cleaning, removal of biological growths and graffiti from stones, cleaning of bronze and iron artifacts and related aspects of laser conversion of unstable minerals, removal of calcareous stratification from wall paintings, and other features.