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1.
Renzo Salimbeni Roberto Pini Salvatore Siano Giancarlo Calcagno 《Journal of Cultural Heritage》2000,1(4):2215
The utilization of laser light to produce fine and selective cleaning of superficial deposits and encrustation from stones was originally proposed more than 20 years ago by John Asmus who performed pioneering trials of laser cleaning on stone façades in Venice, Cremona and Padua. The opportunity to collect stone samples from these sites allowed us to carry out an original study aimed at evaluating the conservation state of stone surfaces cleaned 10–20 years ago by means of three different techniques: Nd:YAG laser radiation, micron sandblasting and chemical pads. Samples of various stone types, as Istria limestone, Botticino limestone and Nanto sandstone were collected and examined by means of optical and SEM microscopy, FT/IR, and EDAX analyses. The results provided preliminary indications that the state of conservation of stone surfaces previously subjected to laser cleaning is generally better in comparison with those which concurrently underwent mechanical and chemical cleaning. 相似文献
2.
Within the framework of a European project, three cleaning laser devices are tested to evaluate the influence of different parameters on stone cleaning rate and efficiency. The project objective is to design a large surface-cleaning laser. One of the devices is a prototype with some technological improvements compared to the lasers used today for restoration. The tests are performed on limestone and sandstone covered with various dirt layers. The influence of fluence, water spraying, spot area, frequency, as well as particle emission rate is investigated. Results allow a comparison of the importance of each parameter and confirm the increase in cleaning speed of the new prototype. Nevertheless, it can be concluded that an automatic device will be suitable to attain a cleaning speed competitive with other traditional cleaning techniques. 相似文献
3.
Laser cleaning of ancient marble and stone monuments is nowadays a well-accepted procedure in conservation. Operators and specialists are presently divided between those giving maximum confidence to this method of cleaning and others who, in contrast, are strongly critical and emphasise possible drawbacks and damages caused by laser. As any other method of cleaning, laser also offers advantages but at the same time is limited by drawbacks. Most conveniently, it should be integrated with the other methods. On the basis of the above considerations, the authors are proposing a combined procedure using laser cleaning as a first step – in this way removing the relevant part of black gypsum encrustation – followed by chemical methods as a final step. The latter, conveniently, could be accomplished by means of anion exchange resins, better than ammonium carbonate. An experimental check-up was made of four different methods applied on three different lithotypes on the façade of the Florentine Cathedral. Laser, micro-sandblasting, ammonium carbonate and sodium EDTA were the cleaning methods compared, whilst Carrara marble, green Serpentine (Verde di Prato) and a red limestone were the three lithotypes. Results are commented by showing differences in the advantages and drawbacks among the different methods on the various lithotypes. 相似文献
4.
The development of laser cleaning as a conservation treatment has imposed a need for the evaluation and assessment of other cleaning techniques. The use of more traditional methods like abrasive cleaning, steam cleaning and chemical cleaning has relied so far on visual assessment, unlike much of the research applied to laser cleaning. A conscientious use of these cleaning methods requires their assessment as well as the need for a comparison based on a common methodology. A topographical assessment of laser cleaning, abrasive cleaning, steam cleaning and chemical cleaning (using hydrofluoric acid, ammonium carbonate and EDTA) is presented. Topographical variations induced on marble, oolitic limestone and architectural terracotta surfaces are assessed by means of light interferometry, showing the potential of this non-contact and non-destructive technique for surface studies in conservation. The comparison between cleaning treatments is based upon key parameters associated with cleaning surfaces. The aesthetic impact of these treatments is verified by means of optical microscopy and quantified by colour measurement. Chemical analysis of the cleaned surface (EDS) is performed to investigate the removal of surface pollutants and the presence of residues. Finally, petrographical analysis was used to investigate the removal of pollutant layers and its effect on surface texture. 相似文献
5.
Laser cleaning was applied to remove aged and soiled oil paints of the 19th century from weathered, brittle sandstone surfaces. In contrast to other tested cleaning methods, the laser technique allows the removal of the oil paint layers with a minimum of material loss in brittle zones. The cleaned test areas have been investigated by optical and scanning electron microscopy as well as by colour measurements. The investigations have shown that the dirt and the oil paint layers can be removed by laser cleaning without affecting the original sandstone surface and that the pores can be opened again. The brown shade after cleaning is not caused by laser interaction with the sandstone surface but by historic impregnation with linseed oil. Immediately after cleaning, a treatment with chemical consolidants is necessary to preserve the brittle sandstone surface. Sustainable consolidation could be problematic in some areas, because the laser cleaning also preserves heavily damaged, crumbling zones of the carvings. For economic reasons, laser cleaning should be applied only in the most endangered zones of carvings and combined with classical methods (organic solvents and scalpel). 相似文献
6.
《Journal of Cultural Heritage》2014,15(3):258-265
Lasers have served as cleaning tools for historical objects and artworks for about 40 years. In many cases, superior results of laser cleaning were achieved with respect to traditional methods. In this technique, contaminations on the surface of the object are ablated by laser irradiation. In order to apply laser cleaning method to fragile materials such as paper made of cellulose or parchment, heat deposition to the bulk should be minimal, to prevent damage. In this work, it is demonstrated that laser pulses with femtosecond (fs) duration can exhibit non-thermal ablation of contaminants on paper samples. In particular, laser cleaning studies are concentrated on paper samples with sizing. Fs laser cleaning is performed on artificially soiled and aged samples, as well as on historical ones. The laser used in the experiments has pulse duration of 550 fs and 1030 nm center wavelength. The fluence of the laser is varied and the post-cleaning statuses of samples are investigated. The analyses are color changes, fiber integrity, chemical composition changes and mechanical strengths. These results show that fs lasers can be very efficient in cleaning paper samples, yielding minimal discoloration and no damage to fibers distinguishable on microscopic examination. The presence of sizing also provides further protection against possible side effects. 相似文献
7.
The historical paper samples from XIII–XIX c. are characterised by means of techniques of the optical spectroscopy. The influence of pulsed laser cleaning by means of the Q-switched Nd:YAG laser at 532 nm on the spectra and also cleaning results of stained paper documents are reported and considered. In the absorption spectra, the minima around 280 and 370 nm are identified and luminescence reveals a characteristic band centred around 430 nm. The laser cleaning diagnosed by the recording of the LIF spectra with 266 nm excitation shows a profile of increasing intensity and preserved structure. The LIPS spectra reveal sharp emission lines recorded at 612.5, 644.2, 646.5, 671, 714.9, 720.2 nm (Ca I), 589.4, 616.4, 780 nm (Na I), and 766.5: 769.9 nm (Mg I) which are ascribed to the surface contaminations. The intensity decrease of these peaks is in accordance with successive laser pulses and monitors the cleaning progress of the stained paper. 相似文献
8.
An investigation has been undertaken into the effect of wavelength in the laser cleaning of parchment. Tests have been carried out using the fundamental (1 064 nm), second harmonic (532 nm) and fourth harmonic (266 nm) outputs from a Q-switched Nd:YAG laser (pulse length 10 ns). Initial testing was carried out on new parchment to characterise the damage caused by overcleaning. The fluence and wavelength of the laser beam were then optimised so that any damage to the parchment or loss of ink during dirt removal from a late eighteenth century parchment document were minimised. The cleaned surfaces were examined by optical and scanning electron microscopy and analysed by measurement of the shrinkage temperature of cleaned collagen fibres. The laser-cleaned areas were compared with uncleaned areas and areas cleaned by traditional techniques. 相似文献
9.
Potentials and limitations of the near-UV pulsed laser cleaning of parchment (wavelength 308 nm, pulse duration 17 ns) are demonstrated by the application of scanning electron microscopy (SEM), colour metrics and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) at model contamination/pigment/parchment systems. Pigment-binder systems stable and unstable against near-UV laser treatment could be identified. A chemical degradation threshold fluence of a goat parchment model substrate was determined which practically coincided with its ablation threshold fluence. This indicates that the fluence range of destructionless laser cleaning at 308 nm is almost not impaired by chemical modfications below the ablation limit. Nevertheless, spectroscopic diagnostics are necessary to guarantee destructionless cleaning for practical cases where the chemical conversion threshold fluence deviates from the ablation threshold to lower values. 相似文献
10.
The Church of the Maddalena was built between 1763 and 1778 by Tommaso Temanza. The building has a central plan and is surmounted by a copper-covered brick masonry dome. The conservation work conducted on the façade has highlighted the superb quality workmanship of the Istrian stone surfaces, which feature extremely fine grain, perfectly regular tooth-chiselling. This finish has led, however, to very specific conditions of decay and laser treatment provided appreciably better results than traditional chemical and mechanical methods. In addition to laser, however, other methods of cleaning were used in order to find the best response to each of the various situations encountered. Indeed it should be emphasized that in restoration it is often appropriate to exploit the potential of several systems, combining their action on the basis of careful preliminary analyses. 相似文献
11.
Within the conservation programme of the mausoleum of Theodoric, located in Ravenna, Italy, we applied a new cleaning procedure based on the use of a recently developed Nd:YAG laser system, suitably equipped in this case with long optical fibre cables for the transmission of laser radiation to work sites on the façade. The intervention of the laser technique was required to complete the cleaning of a decoration surrounding the monolithic dome, after conventional cleaning methods had been applied with unsatisfactory results. Preliminary laboratory analyses on stone samples collected from the dome and subjected to laser treatment indicated that this technique was effective and could fully preserve the lime–Ca oxalate film existing below the thick layer of black crusts. Before starting the operative phase on the mausoleum, it was necessary to solve the practical problem of keeping free access to the monument during cleaning operations, which hindered the location of the laser in close proximity to the sites to be cleaned. This was achieved by preparing long fibre cables (up to 50 m) which permitted the successful completion of the cleaning while leaving the laser body far away from the dome. 相似文献
12.
An innovative laser restoration tool for non-contact cleaning of painted artworks is developed. Accurate beam manipulation techniques in combination with on-line detection make the system suitable for selective cleaning of delicate surfaces. The utilisation of lasers obviates the use of various chemicals, and provides a method to remove layers that are untreatable using conventional methods. The first professional laser cleaning station for paintings is equipped with a modern mechatronic engineering tool for accurate beam manipulation (‘optical arm’). An intelligent combination of software and hardware enables accurate control, necessary to deal with the variable properties of the artworks to be treated. An on-line monitoring system is incorporated, using laser-induced breakdown spectroscopy. The user interface plays an important role in simulating the ‘hands-on’ treatment. In January 1999, the 2-year European co-operative research project ‘Advanced workstations for controlled laser cleaning of artworks’ started. The research objective is to define the boundary conditions in which laser cleaning with the present technology can be safely applied. 相似文献
13.
On-line monitoring or even closed-loop control is necessary to avoid over-cleaning in case the ablation process is not self-limiting. Therefore, the laser-induced breakdown spectroscopy (LIBS) was used. Basic investigations were carried out on original sandstone samples (Elbsandstein) with strong encrustations as well as medieval stained glass samples (13th century from Cologne Cathedral). The spectroscopic study has shown that the plasma emission can be used for determination of the elemental composition of the ablated material. The plasma was initiated by 248-nm pulses of an KrF-excimer laser (30 ns FWHM). For the spectroscopic analysis, a grating spectrograph in combination with an optical multichannel analyser was used. For the glass and stone samples we obtained a continual alteration of the LIBS spectrum (vanishing of peaks and generating of new element peaks) during the removal process. Thus, certain element peaks can be used to distinguish between encrustation layer and valuable underlying material. To show the potential of LIBS we designed an experimental laser cleaning set-up including closed-loop LIBS control and demonstrated successful automatic cleaning of an original glass fragment. 相似文献
14.
A collaborative project between the Materials Department of Imperial College, the Victoria & Albert Museum, Natural History Museum and the Tate Gallery was initiated with the objective of introducing laser cleaning in these London-based museums and establishing a long-term research collaboration. An access to these material conservation departments means that materials like traditional statuary materials, heavily corroded metals, ivory, palaeontological samples, textiles, stained glass, plaster and some modern materials can be used to investigate the usefulness of laser cleaning and study their effects using a wide range of analytical techniques. 相似文献
15.
A medieval wooden panel chamber was rediscovered during reconstruction of the Tetzelhouse in the Saxon town of Pirna. Ceiling and walls are made from 600-year-old fire wood panels fitted together. The complete removal of layers (limewash, plaster, glue and dirt) from the wall panels was the precondition for conservation of the wood panels and for the restoration of the wooden panel chamber. The cleaning was carried out with a pulsed Nd:YAG laser after basic investigation of ablation mechanisms of the layers on the old wood. All layers of the different materials were removed both from the normal surface and out of depressions and woodworm holes with a special range of laser parameters, without damaging the wood. Within this range of parameters the laser cleaning is a self-limiting process. The health hazard from emitted waste products were determined and checked with work place measurements. The laser cleaning of the wooden wall panels was completed in March 1999. A uniform visual impression of all panels was obtained with a warm wooden colour tone. 相似文献
16.
A series of tests has been conducted to evaluate the potential for using a Q-switched Nd:YAG laser (wavelengths 1 064, 532 and 266 nm) to clean both new and naturally aged cotton textiles. Tests have been carried out on i) plain weave and velvet cotton and ii) new and naturally aged cotton samples to investigate the possible roles of weave structure and ageing in the cleaning process. Cleaning trials have been carried out on artificially soiled new cotton and compared with results obtained using traditional cleaning techniques: wet cleaning and organic solvent cleaning. Cleaned surfaces were examined using optical and scanning electron microscopy. 相似文献
17.
SMART CLEAN is an innovative Nd:YAG laser system that has been designed to optimize laser cleaning procedures, especially for the treatment of altered stone surfaces. The project, originated by the co-operation of researchers and enterprises involved in optoelectronics system development, was aimed at improving the intrinsic features of the laser source, as well as some practical aspects, in order to facilitate laser application in the restoration yard. Emission characteristics were suitably tailored to obtain effective removal of alteration layers, and to minimize possible side effects. In particular, the pulse duration of the SMART CLEAN laser was set at 20 μs, by means of a proprietary design of the power supply. This was in order to reduce the risk of both mechanical and thermal damage to the artwork substrate, which is more likely to occur with short and long laser pulses, respectively. Moreover, this pulse duration permitted a reliable transmission of high laser energy through long optical fibres (50 m), which allowed easy cleaning operations on façades. The laser system was tested on a large variety of lithotypes and in operative cleaning interventions on Italian monuments. 相似文献
18.
The self-limiting effect during laser cleaning only occurs in a limited amount of specific applications in restoration (e.g. removal of black crust from white marble). In all the other cases, a control of the removal process will be necessary either by the operator himself or by the employment of sensor equipment. Various methods, mainly spectroscopic (e.g. LIBS), have been investigated and proposed by others. Despite the fact that these have been shown to be promising, they all have in common rather high investment cost close to that of the cleaning equipment. Furthermore, this highly sophisticated control equipment is not easy to handle by conservators in practice. As an alternative low-cost method, we employed a simple photodiode to detect the scattered light from the irradiation area on the artwork surface. In many cases, this signal contains several pieces of information on the layer just being removed. The scattered radiation detected by the photodiode originates from the laser-induced plasma as well as reflected laser radiation. A separation, if necessary in order to separate the information, is possible by spectral filters. First applications during laser cleaning of corroded metal, encrusted glass and stone were promising. It has turned out that there is a distinct influence on the scattered light amplitude or even the pulse-bandwidth once the laser has removed the encrustation completely. The corresponding signal can be used in a closed loop control or for online monitoring. 相似文献
19.
Ramadan Abd-Allah 《Journal of Cultural Heritage》2013,14(2):97-108
The aim of this study is practically to establish a chemical strategy for cleaning soiled deposits and encrustations on archaeological glasses. Investigations were performed on a series of Roman glass samples (Fragments and complete objects) coming from different excavations in northern Jordan. The chemical composition of the glass samples was determined by X-ray fluorescence spectrometer (XRF) analysis technique, whereas X-ray powder diffractometer (XRD) and Energy dispersive X-ray (EDX) methods were used to determine the mineralogical and elemental composition of the soiled deposits and encrustations on the glass surfaces. Furthermore, Scanning Electron Microscopy (SEM) examination and optical assessment were performed before and after cleaning glass. The glass samples were subjected to different cleaning protocols such as Calgon (Sodium hexametaphosphate), ethylenediaminetetraacetic acid (EDTA) at different pH values, citric and tartaric acids and piranha solution (a solution of sulphuric acid and hydrogen peroxide). Sepiolite poultices soaked by chemical agents were the most suitable methods used for applying chemical solutions on the glass surface. It can be concluded that EDTA is generally accepted as the most effective chelating agents recommended for cleaning encrustations on durable glass. It was more effective and safe at neutral pH with low concentrations around 5 to 7%. The calcareous crusts can safely be removed by using a piranha solution. Citric and tartaric acids appeared a moderate efficiency on cleaning weathered and stable glass. Calgon has a tendency to damage corroded and iridescent surfaces, and should be avoided when cleaning weathered glass. 相似文献
20.
《Journal of Cultural Heritage》2007,8(2):119-125
In the present article we report a study on some sodium dodecyl sulphate/propylene carbonate based aqueous micellar solutions developed with the aim of setting up a nanotechnological cleaning system to remove naturally aged polymeric acrylic layers from the surface of the wall paintings in the Old Sacristy of Santa Maria della Scala in Siena (15th century). Being these systems mainly composed of water (more than 70% by weight), the cleaning of the painted surface have been performed with low environmental impact, due to the small amount of the pure organic solvents used (always less than 25% by weight). Furthermore, the aqueous phase constitutes a hydrophilic barrier to the penetration of the hydrophobic acrylic materials into the porous support. Fourier Transform InfraRed spectroscopy (FTIR), Scanning Electron Microscopy coupled with Energy Dispersive X-rays analysis (SEM/EDX) and in situ capillary water adsorption measurements indicated the efficacy of this cleaning procedure. Finally, the chemical diagnostics investigation enabled to ascertain the presence of both salts (nitrates and gypsum) and the acrylic polymeric material. 相似文献