The assessment of five different laser treatments in the conservation of wall paintings was devised on the basis of the surface temperature monitoring by infrared thermography (IRT), ultraviolet-induced fluorescence-visible (UV-VIS) imaging, and optical coherence tomography (OCT). A series of yttrium-aluminum-garnet (YAG) lasers were tested for removal of shellac layers from wall painting mock-ups. The mock-ups were realized as buon fresco with different mineral based pigments (earths and iron oxide) on a lime-and sand-based mortar. After the carbonatation process, all the samples were treated with shellac (5% in ethanol). The effects of neodymium (Nd):YAG, holmium (Ho):YAG, and erbium (Er):YAG laser sources, in different operative modes, on average temperature of the surface, color, and morphology were inspected with complementary sensors. The results show the necessity to adopt a combined approach in establishing safe laser operating conditions to avoid any undesired effects induced on the artefacts by the laser treatments. We demonstrate, for the first time, the performance of the Ho:YAG laser in the removal of a conservation treatment.

Fiber optics reflectance spectroscopy (FORS) and visible and near-infrared (VNIR) hyperspectral imaging (HSI) were applied to assess and control the laser cleaning process of a deeply darkened limestone surface collected from the historic entrance gate of Castello Svevo, Bari, Italy. Both techniques enabled us to verify the different degree of removal of a thick deposit of black crust from the surface of the walls. Results obtained were in good agreement with those of previous studies of the elemental composition achieved by application of laser-induced breakdown spectroscopy (LIBS). Coupling FORS and VNIR-HSI provided important information on the optimal conditions to evaluate the conservation status and determine the more appropriate level of cleaning restoration, thus avoiding over- and/or under-cleaning. maging spectroscopy was used to obtain maps of areas featuring the same or different spectral characteristics, so to achieve a sufficient removal of unwanted layers, without modifying the surface underneath, and to increase the efficiency of traditional cleaning techniques. The performance of the combined non-invasive approach used in this work shows promise for further applications to other types of rocks and highlights the potential for in situ assessment of the laser cleaning process based on reflectance spectroscopy.

Architectural surfaces, façades and monuments made of stone are subject to alteration/decay phenomena due to natural or anthropic agents. Salts, black crust formations, biodegradation and graphic vandalism (writing, drawing and inscription) are responsible for detrimental effects as they can accelerate the stone decay leading to considerable loss in value and significance. Cleaning approaches are usually based on mechanical (e.g. sandblasting) or chemical methods, but they are potentially harmful for operators and the environment. In this paper, the feasibility of a new laser system for the removal of spray paints and felt-tip permanent markers from marble and sandstone is investigated. The laser system INFINITO (by El.En. SpA) is an active fiber laser operating at 1064 nm (Yd:YAG source) consisting of a lightweight and compact instrument which lends a high portability and adaptability to site work. INFINITO permits fine tuning of the laser parameters and allows an automatic scanning of the surface thanks to an effective mirror handling system (i.e. the scanned area size is up to 40x40 mm2 with a lens focal length of 250 mm). This study has been devoted to demonstrate the capability of the system to control the level of cleaning ranging from thinning of the paint to complete cleaning of the surfaces. Consequently, the ablation and thermal effects on the materials were investigated and the evaluation of the damage threshold of the stone substrate to ensure a safe and sensitive cleaning method has been carried out. Laser parameters such as power, fluence, repetition frequency, spot size and scanned area size were varied in a systematic analysis in order to achieve the desired cleaning performance.

This work is focused on the conservation-restoration workscarried out on the Speranza, monumental sculpture of the 19th century placed inside the English Cemetery in Florence. The statue was covered by scattered greenish and black-grayish patinas mainly due to the biological growth. Optical microscopy, culture-based methods and CF-PAM imaging (Pulse Amplitude Modulated fluorometry of the Chlorophyll Fluorescence) were used to characterize the biodeteriogens, while the study of the stone material and of the decay layers was performed trough microstratigraphic observations and X-ray diffraction analyses. Laser cleaning trials were carried out using different wavelengths (1064 nm and 532 nm) and pulse durations. The optimization of the laser parameters was performed taking into account the results obtained from the stratigraphic layers observations of the thin cross-sections of the stone material and real time CF-PAM imaging of the phototrophic presence.The study allowed improving, planning and accomplishing of the laser cleaning treatment of the whole statue.

The essay presents the project and the results of the restoration works on the stone elements and decorated surfaces of the façade and the two courtyards of the Istituto degli Innocenti in Florence. The building, having at length been subjected to atmospheric agents and acts of vandalism and having been interested by some interventions in the past centuries, showed an accentuated degradation. Yet, from the planning of the intervention, the work group recommended the use of the laser: therefore, an accurate methodology has been determined in order to optimize the timing, the procedures and the results of the intervention. First, a cleaning with traditional tools (chemical and mechanical) has been undertaken on the most compact areas; then, the Laser technique has been used on the most decayed and delicate portions, with black crusts and heavy degradation, employing two different Q-switch wavelengths - A) 1064 nm and B) 532 nm - and diversifying the energy, the frequency and the spot diameter relating to the typology of surfaces and their alterations.

The cleaning of plasterworks could be often complicated by the presence of surface materials, originating from molding and patinas. Lasers allow dry cleaning with high selectivity, but guidelines for the cleaning of plasterworks finished with intentional patinations are unavailable. A set of tests was conducted to identify the range to perform a correct laser cleaning on plaster model samples patinated with beeswax, de-waxed shellac, Arabic gum and boiled linseed oil, using three laser systems: Nd: YAG devices at 1064 nm and 532 nm, both in Q-Switch, and a Er: YAG at 2940 nm, starting with the smallest values of fluence and repetition rate. The effects of laser cleaning on model samples were evaluated with colorimetric, gloss, contact angle measures and stereo-microscopic observations; considering the results obtained, damage was identified on the patina and/or on the plaster substrate with the Er: YAG system, starting at a minimum of 0.50 J/cm2 and a repetition rate of 1 Hz, with the exception of the shellac treatment, which showed neither morphological or optical variations, up to the fluence of 1.25 J/cm2 with repetition rate to 5 Hz. The shellac had variations in color with the Nd: YAG at 1064 nm @ 0.79 J/cm2 and a 2 Hz; no chromatic variations resulted for the remaining three patinas in the range of fluences tested, with values between 0.31 J/cm2 and 1.1 J/cm2, with repetition rate up to 3 Hz. No effects were detected when cleaning with the Nd: YAG at 532 nm, which was effective to 2.4 J/cm2 with increasing repetition rate, up to a maximum of 2 Hz.

The main aim of this work is to present the results of an experimentation carried out by a restoration graduation thesis, at Brera Academy Fine Arts in Milan. This thesis had the purpose of verifying the possibility of performing a descialbo operation with different sources laser on plaster artifacts. Plaster model samples were designed and built with the traditional molding technique. On their surfaces, was applied a thin layer of shellac and, then, three different types of scialbo were laid out. The laser ablation tests with the two different sources - neodymium source and holmium source - were performed using different operating ways (dry and wet) in order to identify the appropriate fluence parameters for removing the scialbo layer. The effects of irradiation and the different levels of cleaning were evaluated with the aid of colorimetric analysis and with the observation of cross-sections by Optical Microscopy

Cleaning of metallic threads has been a recurrent dilemma in historical textile conservation. Careful selection of restoration methods is in fact required because decayed metallic threads are wrapped around natural textile fibers. This article synthesizes the results of a conservation study undertaken at the Accademia di Francia in Rome of a silk velvet cope. The artefact, a silk velvet cope with different types of metallic threads, dating from the 15th century, coming from the collection of the Musée des Tissus de Lyon in France, was the subject of experimental cleaning tests using laser ablation and other technologies to ascertain the most effective method of cleaning compound textiles. Two laser instruments with variable wavelengths and pulse length were tested: laser Nd:YAG, QS at 1064 and 532 nm, and the laser Nd:YAG, LQS at 1064 nm. The laser tests were focused on the cope's metallic fringes, presenting three types of wires of different shape, composition and state of degradation. Parameters such as frequency, pulse, and beam size were adjusted to match the small size of the metal strips and to avoid any damage to the silk fibers over which they are wrapped. The effectiveness of the cleaning levels of the metallic threads have been evaluated through SEM-EDS, as well as the evidence of any damage to the organic fibers.

This paper presents a laboratory-scale experimental investigation about the laser cleaning of diagnostic first mirrors from tokamak-like contaminants, made of oxidized tungsten compounds with different properties and morphology. The re-deposition of contaminants sputtered from a tokamak first wall onto first mirrors' surfaces could dramatically decrease their reflectivity in an unacceptable way for the proper functioning of plasma diagnostic systems. The laser cleaning technique has been proposed as a solution to tackle this issue. In this work, pulsed laser deposition was exploited to produce rhodium films functional as first mirrors and to deposit onto them contaminants designed to be realistic in reproducing materials expected to be re-deposited on first mirrors in a tokamak environment. The same laser system was also used to perform laser cleaning experiments, exploiting a sample handling procedure that allows one to clean some cm(2) in a few minutes. Cleaning effectiveness was evaluated in terms of specular reflectance recovery and mirror surface integrity. The effect of different laser wavelengths (lambda = 1064, 266 nm) on the cleaning process was also addressed, as well as the impact of multiple contamination/ cleaning cycles on the process outcome. A satisfactory recovery of pristine mirror reflectance (>= 90%) was obtained in the vis-NIR spectral range, avoiding at the same time mirror damaging. The results here presented show the potential of the laser cleaning technique as an attractive solution for the cleaning of diagnostic first mirrors.

Laser cleaning of bronze artefacts is a very promising conservation approach and its wider distribution would benefit from further studies of its advantages and drawbacks. Some important references are available, yet laser cleaning cannot be considered a traditional method for bronze surfaces. In this paper, we report on the evaluation of cleaning tests performed on an important statue of Napoleon, depicted as Mars the Peacemaker, cast by Righetti in 1811 after a model by Antonio Canova. The sculpture is exposed to the outdoor environment in the main courtyard of the Brera Gallery, Milan, Italy. An analytical survey of corrosion products was carried out using X-ray diffraction, micro-Fourier transform infrared spectroscopy (?FTIR), and ?Raman spectroscopy; and scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis was applied to cross-sections. The results showed the ubiquitous presence of brochantite Cu4(SO4)(OH)6. Antlerite Cu3SO4(OH)4 is also occasionally present. Residues of an past conservation treatment (Incralac®) and of proteins were detected by ?FTIR. Laser cleaning tests were carried out with an El.En. Combo laser, both in long Q-switched and short free-running regimes. Evaluation of the effects of cleaning was carried out with a portable microscope and a reflectance colorimeter. Moreover, a portable FTIR spectrometer was used in order to evaluate the presence of coating residues and corrosion products after cleaning. Electrochemical impedance spectroscopy was used in situ on a selection of the tested areas in order to characterize the effect of laser cleaning on the rate of corrosion. A specially designed contact probe was used for measurements in the frequency range 100 kHz-10 mHz both before and after cleaning.

The patina, is the result of a large number of chemical, electrochemical and physical processes which occur spontaneously during interaction of metal surfaces with the environment. In this work we want to analyze and remove the patina in artefacts, exposed to atmosphere for various decades. Here, experimental results about the laser cleaning of bronze coins by KrF (248 nm) and Nd:YAG (532 nm) lasers are reported. Both laser wavelengths were efficient to reduce the chlorine concentration on the surface of the coins more than 80 %, as demonstrated by Energy Dispersive X-Ray Fluorescence analyses.

The Er:YAG laser has proven particularly efficient in cleaning procedures of works of art. The removal of the superficial deposits is achieved through melting, thermal decomposition and evaporation. However, the energy absorbed by vibrational modes is dissipated as heat, increasing the temperature of the surface coating that could cause damage on the object. The aim of this study was to evaluate the temperature increase induced by a Er:YAG MonaLaser (LLC., Orlando, FL, USA). To that purpose, we designed a dedicated device to perform the tests in an inert atmosphere or with a wetting agent, to measure the radiant energy per laser pulse. Tests were carried out both on graphite, which absorbs IR radiation and showed a very intense flash emission, and on different kind of samples representative of materials with different levels of conductivity and thermal diffusivity. Results obtained showed that the temperature increase in the irradiated surface depends on the substrate but never causes

Il restauro conservativo delle facciate della "Ca Granda" in fregio alle vie Festa del Perdono e San Nazaro, attualmente in corso, è un appalto pubblico affidato con procedura di sponsorizzazione che prevede una durata dei lavori di circa quattro anni ed una ripartizione in sette lotti d'intervento1 (fig. 1). Proprio per la specificità del cantiere e dell'appalto (Tabella 1) e, naturalmente, dell'approccio metodologico utilizzato, sin dal 2009 ci si è trovati immersi in una realtà complessa e polifonica che ha richiesto di iniziare un dialogo con la fabbrica che comprendesse differenti temi.

This work, aimed at quantifying the morphological variations induced by laser cleaning on stone materials, represents a very first attempt for a now quantitative means to reveal changes in stone surfaces. It is a, three-dimensional survey carried out by means of laser micro-profilometry and completed by statistical data processing. The acquisition and successive computation is performed on small selected areas both before and after the cleaning process.

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 facades 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. (C) 2000 Editions scientifiques et medicales Elsevier SAS