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In this work, warm white (3,000 K) LEDs were used for investigating accelerated ageing of different classes of natural terpenoid compounds. In particular, colophony, sandarac, shellac, and mastic resins were considered. Maximum total irradiance of 80 Mlxh was used, which can be compared to about 130 years of exposure in recommended museum conditions. Moreover, another set of the same resins was kept in darkness conditions in order to assess kinetic differences. Raman spectroscopy was employed to assess molecular changes occurring in resins structures during both dark and light ageing. Spectroscopic information was achieved through a portable Raman scanner provided with a narrow-b and CW diode-pumped Nd:YAG (1,064 nm) laser and an NIR spectrometer equipped with an InGaAs linear array. Vis-LED light appears to be suitable to avoid yellowing in the case of mastic and colophony resins suggesting that it is advisable to use this light with respect to traditional halogen lamps for illuminating museums and art galleries. Conversely, the ageing process of sandarac and shellac appears not to be particularly affected by the UV radiation. Raman spectroscopy in combination with multivariate analysis (principal component analysis) was able to provide information about the ageing process of colophony both in light and dark conditions. [ABSTRACT FROM AUTHOR]

The periodical removal of biodeteriogens is a fundamental need for the preservation of outdoor stone cultural heritage, which is stimulating significant efforts toward the development of low-impact conservation strategies. In the present work, the potential of laser removal of Verrucaria nigrescens Pers. from Carrara marble and the evaluation of the associated biocide effect on the organism residues embedded in the surface texture and through the outer porosities of the stone substrate were investigated. The fundamental wavelength of Nd:YAG laser (1,064 nm), commonly used in stone cleaning, and its second harmonic (532 nm) were comparatively tested. The phenomenology of laser treatments carried out in different irradiation conditions was characterized using optical, epifluorescence, and electron microscopes along with chlorophyll fluorescence with pulsed amplitude-modulated imaging. The results achieved show that 532 nm can provide significant advantages with respect to 1,064 nm. The potential of the latter against the biodeteriogens appears rather limited because of the low optical absorption, whereas the former can allow effective and practicable laser treatments, which disclose a significant application perspective. [ABSTRACT FROM AUTHOR]

The removal of overpaintings from valuable easel paintings represents a very difficult challenge, which is traditionally approached using solvents and moderate mechanical actions. Here, we explore for the first time the potential of Long Q-Switching Nd:YAG (1,064 nm) laser with a pulse duration of 120 ns for selective ablation of overpainting layers. Mock-ups were prepared in order to approach in a systematic way a concrete uncovering problem concerning a modern painting on canvas. The former were prepared according to the stratigraphy and material compositions of the latter, as measured using optical and ESEM-EDX microscopy along with infrared and portable Raman spectroscopy. The parameterization achieved on the mock-ups allowed interpreting and maximizing the selectivity of the laser conservation treatment carried out on the real case. [ABSTRACT FROM AUTHOR]

Here, we investigated the potential of laser removal of iron-rich dark films from weathered granite substrates, which represents a very difficult conservation problem because of the polymineralic nature of the stone and of its complex deterioration mechanisms. As often occurs, biotite was the most critical component because of its high optical absorption, low melting temperature, and pronounced cleavage, which required a careful control of the photothermal and photomechanical effects to optimize the selective ablation of the mentioned unwanted dark film. Different pulse durations and wavelengths Nd:YAG lasers were tested and optimal irradiation conditions were determined through thorough analytical characterisations. Besides addressing a specific conservation problem, the present work provides information of general valence in laser uncovering of encrusted granite. [ABSTRACT FROM AUTHOR]

The potential of laser ablation in conservation of paper artifacts of cultural interest is under investigation since the second half of nineties. However, the works carried out on the topic are relatively a few as compared with those dedicated to stone, metal and painted artworks. Furthermore, in the latter cases, widespread applications have been successfully carried out, whereas laser cleaning of aged paper is still far from the conservation practice. There are serious risks to produce short- and/or long-term chemical alterations and/or mechanical damages at relatively low fluences. Here, we report a systematic investigation on laser removal of mold growths from prepared and naturally aged paper samples. Fundamental wavelength and second harmonic of QS Nd:YAG laser are tested and compared through optical and spectroscopic characterizations. This allowed defining optimized irradiation conditions and foreseeing further improvements from pulse duration optimization. [ABSTRACT FROM AUTHOR]

The present work focuses on the potential of 3D digital microscopy for assessing micro-morphological features during laser cleaning treatments of artworks. This application requires preliminary optimization studies aimed at defining operative irradiation parameters and practicable degree of cleaning, as well as in situ diagnostic assessments during the restoration work. To this goal, we developed and tested a dedicated 3D digital microscope by implementing the 'shape-from-focus' technique. The significant potential of this instrument, which provides textural and chromatic information, was proven for the phenomenological characterization of black crust removal from stones, earthy concretion from bronzes and dark varnish from easel paintings. Comparative measurements using 3D digital microscopy and contact microprofilometry were performed after laser cleaning tests of prepared samples, genuine archaeological bronze artefacts and a stone sculptural element from Florence's Dome. The results achieved demonstrate the effectiveness and reliability of the novel approach and the advantages it provides with respect to alternative techniques, which will allow the methods to be used in the wider restoration community. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Neutron diffraction experiments have been performed on laboratory-prepared samples of copper alloys to determine their microscopic phase characteristics. The aim of this experiment is to set up a database that can be used in future neutron diffraction measurements on metal samples mainly of archaeological interest. [ABSTRACT FROM AUTHOR]

We report the development of a novel portable and low-cost laser induced plasma spectroscopy (LIPS) system and describe the application method for quantitative characterisation of quaternary copper alloy artefacts. The device was carefully calibrated and phenomenologically characterised using a set of reference samples. The reliability of the quantitative measurement of the depth profile and bulk compositions was assessed through crossed comparisons with traditional analytical techniques. Finally, the LIPS system was applied to investigate a museum figurine of unknown origin composed of several pieces, which is representative of a typical authentication problem. [ABSTRACT FROM AUTHOR]

The present work focuses on the main phenomenological features of stone cleaning by lasers. These are the removal rate, cleaning degree, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted stone artifacts and two sets of standards in order to derive general behaviors through repeatable measurements. The analysis of the irradiation tests provided quantification of the different efficiencies, cleaning degree, and chromatic appearances associated with the fundamental harmonic of Q-switching, long Q-switching, and short free-running Nd:YAG lasers (1064 nm), as well as with the second harmonic of Q-switching sources (532 nm). [ABSTRACT FROM AUTHOR]

We report the results of an analytical investigation on the bronze alloys of the Porta del Paradiso by Lorenzo Ghiberti using a portable X-ray fluorescence instrument. The study was carried out on five panels of the bronze artwork. It provided information on the artist’s selection of the sculptural alloys and on some manufacturing details of interest for understanding the development of the art foundry during the early Renaissance. [ABSTRACT FROM AUTHOR]

Neutron radiation meets the demand for a versatile diagnostic probe for collecting information from the interior of large, undisturbed museum objects or archaeological findings. Neutrons penetrate through coatings and corrosion layers deep into centimetre-thick materials, a property that makes them ideal for non-destructive examination of objects for which sampling is impractical or unacceptable. A particular attraction of neutron techniques for archaeologists and conservation scientists is the prospect of locating hidden materials and structures inside objects. Time-of-flight (TOF) neutron diffraction allows for the examination of mineral and metal phase contents, crystal structures, grain orientations, and microstructures as well as micro- and macro strains. A promising application is texture analysis which may provide clues to the deformation history of the material, and hence to specific working processes. Here we report on instructive examples of TOF neutron diffraction, including phase analyses of medieval Dutch tin-lead spoons, texture analyses of bronze specimens as well as of 16th-century silver coins. [ABSTRACT FROM AUTHOR]

Non-destructive neutron diffraction techniques were applied to determine composition and microstructure data, and hence to derive information on manufacturing techniques of Picenum bronze artefacts. Furthermore, texture analyses were carried out on standards and suitable ancient artefacts to investigate their potential role in archaeometallurgical studies. This is a first step towards an overall characterization of the bronze collection of the Marches National Museum of Archaeology, Italy, and the analytical demonstration of relations with and differences compared to Etruscan metallurgy. The work is also an example application of the powerful non-destructive archaeometrical approaches provided by time-of-flight neutron diffraction. [ABSTRACT FROM AUTHOR]

Neutrons can be produced in nuclear reactions and used as very versatile probes for condensed matter research. Since their introduction in the 1950s neutron scattering techniques have evolved to be very powerful tools for investigating the properties of condensed matter. Here we present the concept of neutron diffraction and how this technique can be used to address problems in archaeology facilitated by accelerator-based neutron sources like ISIS at the Rutherford Appleton Laboratory in Oxfordshire. The great beauty of neutrons for the archaeologist is that they allow non-destructive testing of intact and original archaeological artifacts and museum objects. [ABSTRACT FROM AUTHOR]

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Investigates the stress generation associated with xenon-chloride (XeCl) excimer laser ablation of polyimide. Adaption of variable blast theory in the condition of laser-target interaction in air; Measurement of acoustic transients propagating inside the irradiated target; Evaluation of the alpha fraction of laser energy transferred to the blast wave.

In this paper, we report the first investigation on the potentials of neutron diffraction to characterize archaeological bronze artifacts. The preliminary feasibility of phase and structural analysis was demonstrated on standardised specimens with a typical bronze alloy composition. These were realised through different hardening and annealing cycles, simulating possible ancient working techniques. The Bragg peak widths that resulted were strictly dependent on the working treatment, thus providing an important analytical element to investigate ancient making techniques. The diagnostic criteria developed on the standardised specimens were then applied to study two Etruscan museum pieces. Quantitative multiphase analysis by Rietveld refinement of the diffraction patterns was successfully demonstrated. Furthermore, the analysis of patterns associated with different artifact elements also yielded evidence for some peculiar perspective of the neutron diffraction diagnostics in archeometric applications. [ABSTRACT FROM AUTHOR]

Focusing, as well as diffraction effects experienced by the stress wave produced by the argon–fluoride excimer laser ablation of corneal tissue have been studied in artificial and real eye samples. The evolution of the laser-induced acoustic front was imaged by means of fast shadowgraphy in an artificial eye model, while the absolute temporal profile of the pressure transient along the optical axis was directly measured in enucleated porcine eyes by a needle hydrophone inserted into the eyeball. Observations pointed out that the finite size of the acoustic source gave rise to diffraction effects during propagation, as the development of a negative tensile phase in the pulse shape, while the spherical shape of the acoustic source produced focusing of the wave front, causing pressure enhancements up to a factor of 3 in real eyes. The implications to surgical laser procedures as photorefractive keratectomy are discussed. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]