Proceedings Volume 7391

O3A: Optics for Arts, Architecture, and Archaeology II

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Proceedings Volume 7391

O3A: Optics for Arts, Architecture, and Archaeology II

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Volume Details

Date Published: 25 June 2009
Contents: 9 Sessions, 33 Papers, 0 Presentations
Conference: SPIE Europe Optical Metrology 2009
Volume Number: 7391

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7391
  • Keynote Presentation
  • Spectroscopy I
  • Spectroscopy II
  • Visualisation
  • Terahertz Imaging
  • OCT
  • 3D
  • Poster Session
Front Matter: Volume 7391
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Front Matter: Volume 7391
This PDF file contains the front matter associated with SPIE Proceedings Volume 7391, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Keynote Presentation
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Paul Gauguin in Brittany
Ever since the dawn of the 20th Century there has been a universal consensus that Alphonse Mucha launched the sensation that became known as Art Nouveau. This event was associated with the appearance of his Gismonda poster promoting the Sarah Bernhardt play of that name in Paris in 1894. At an estate sale in 1954 a small collage bearing a likeness of Mucha's Gismonda was offered. It had been fabricated by gluing slivers cut from sixty postage stamps to a 20cm ceramic tile. Digital computer image enhancement was applied to the collage design, initials on a walking stick from the same estate collection, and the Mucha poster. These geometrical analyses revealed that the collage is more detailed than the Mucha "original". This led to our hypothesis that the famous poster was a hasty photographic plagiarism of the intricate ceramic-tile collage. Image analyses of the initials on the companion walking stick revealed conformity with the famous enigmatic "P GO" monogram of Paul Gauguin. We conclude that Gauguin rather than Mucha created the Gismonda composition. Historical evidence suggests that, while Gauguin was in Brittany recovering from injuries sustained in a fistfight, Annah la Javanese stole his possessions and took them to Paris where her next lover, Mucha, copied the collage and presented it as his original poster design.
Spectroscopy I
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Visible and infrared reflectance imaging spectroscopy of paintings: pigment mapping and improved infrared reflectography
Reflectance imaging spectroscopy, the collection of images in narrow spectral bands, has been developed for remote sensing of the Earth. In this paper we present findings on the use of imaging spectroscopy to identify and map artist pigments as well as to improve the visualization of preparatory sketches. Two novel hyperspectral cameras, one operating from the visible to near-infrared (VNIR) and the other in the shortwave infrared (SWIR), have been used to collect diffuse reflectance spectral image cubes on a variety of paintings. The resulting image cubes (VNIR 417 to 973 nm, 240 bands, and SWIR 970 to 1650 nm, 85 bands) were calibrated to reflectance and the resulting spectra compared with results from a fiber optics reflectance spectrometer (350 to 2500 nm). The results show good agreement between the spectra acquired with the hyperspectral cameras and those from the fiber reflectance spectrometer. For example, the primary blue pigments and their distribution in Picasso's Harlequin Musician (1924) are identified from the reflectance spectra and agree with results from X-ray fluorescence data and dispersed sample analysis. False color infrared reflectograms, obtained from the SWIR hyperspectral images, of extensively reworked paintings such as Picasso's The Tragedy (1903) are found to give improved visualization of changes made by the artist. These results show that including the NIR and SWIR spectral regions along with the visible provides for a more robust identification and mapping of artist pigments than using visible imaging spectroscopy alone.
Spectroscopy II
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UV-fluorescence spectroscopy for identification of varnishes in works of art: influence of the underlayer on the emission spectrum
Mady Elias, Caroline Magnain, Carlos Barthou, et al.
The identification of varnishes may be essential for the choice of the appropriate solvent during their removal by restorers. This recognition is obtained by UV-fluorescence emission spectroscopy with a quasi-monochromatic UVexcitation. A new portable instrument has been developed in order to implement non-destructive, contactless and in situ measurements, providing results in real time. The method is applied to the analysis of a real ancient painting. The resin-based varnish, the recipe and the state of degradation of the varnish are deduced in different locations of the painting by comparison with a database of reference varnishes. Moreover, spectral data are compared with the Fluorescence Lifetime Imaging (FLIM) analysis, performed on the same painting. Different areas containing the same varnish can then be localized on the whole painting. These results show that both UV-fluorescence methods are complementary for rapid and in situ analysis of varnishes of an entire work of art. Nevertheless, the paint layer beneath the varnish modifies the varnish fluorescence spectrum thus complicating its recognition. Indeed, the possible fluorescence of the binder of the paint layer or its reflectance spectrum must be taken into account. A systematic experimental study on fresh and aged model samples made of different varnishes, pigments and binders is presented in this work. It shows that UV-fluorescence emission spectra and diffuse reflectance spectra must be coupled to extract the fluorescence of the single varnish. Both spectra can be recorded by the presented instrument. A new theoretical approach is summarized in order to explain this phenomenon.
The application of visible-induced luminescence imaging to the examination of museum objects
Visible-induced luminescence imaging in the near infrared range (800-1700 nm) can play a key role in the spatial characterization of certain historical blue pigments (principally Egyptian blue, Han blue and Han purple). All three of these pigments show a very strong infrared emission when excited across the visible range. The setup required for this type of measurement comprises a recording device with some sensitivity to near infrared radiation and an excitation source in the visible range. Inexpensive and widely available excitation radiation sources that can be used for this application include fluorescent lamps and LEDs. While visible LEDs do not usually emit infrared radiation, commercially available fluorescent tubes may emit some stray infrared radiation. Although the presence of such stray infrared radiation may in some cases be considered beneficial, allowing the user easily to locate the presence of the pigments under investigation within the composition of the piece, it can be easily removed using a simple subtraction method. This method, based on the measurement of the reflective properties of the surface under investigation in the emission range of the luminescent pigments, is described. The emission results obtained for Egyptian blue, Han blue and Han purple are compared to those of a set of representative historical and modern blue pigments, including manganese blue, which was the only other pigment found to show detectable luminescence properties. Examples of the application of visible-induced luminescence imaging to archaeological objects of the Antonine period (AD 100-200) in the collections of the British Museum are also presented.
Use of visible and infrared reflectance and luminescence imaging spectroscopy to study illuminated manuscripts: pigment identification and visualization of underdrawings
Paola Ricciardi, John K. Delaney, Lisha Glinsman, et al.
Site specific, in situ techniques such as X-ray fluorescence (XRF) and Raman spectroscopy are commonly used to identify pigments on illuminated manuscripts. With both techniques, spectra are usually acquired on visually identified sites thought to be representative of the pigments and mixtures used for the illumination. Such visual inspection may not always ensure an adequate representation of the pigment diversity. Here we report on the application of multispectral (MSI) visible/infrared reflectance and luminescence imaging spectroscopy, along with fiber optics reflectance spectroscopy (FORS) to help determine and map the primary pigments in a late 14th century miniature on vellum, attributed to Niccolo da Bologna and representing the birth of John the Baptist. XRF analyses of visually selected sites found elements consistent with azurite, ultramarine, vermillion, lead white, "mosaic gold" and yellow earth pigments. Visible/infrared FORS analyses confirmed these assignments and showed evidence for the use of organic dyes. The spectral analysis of the MSI-reflectance images gave distribution maps for these pigments (i.e., regions of azurite, ultramarine, vermillion) along with some indication of pigment layering not identified visually. The luminescence image gave a probable map of the organic dye(s). Images acquired in the near- and shortwave-infrared (NIR and SWIR, 750 to 2400 nm) revealed preparatory sketches and illumination techniques. These results show, like those of a prior study carried out on another 14th century Italian miniature, that the combination of low light multi-spectral imaging spectroscopy with FORS provides improved in situ mapping and identification of pigments on illuminated manuscripts.
Double laser LIBS and micro-XRF spectroscopy applied to characterize materials coming from the Greek-Roman theater of Taormina
Maria Francesca Alberghina, Rosita Barraco, Maria Brai, et al.
The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown, in recent years, its great potential for rapid qualitative analysis of materials. The possibility to implement a portable instrument that perform LIBS analysis makes this technique particularly useful for in situ analysis in the field of cultural heritages. The aim of this work is to compare the results, obtained by LIBS measurements with X-Ray Fluorescence (XRF) ones, on calcareous and refractory materials coming from the Greek-Roman theater of Taormina. Calibration curves for LIBS and XRF were obtained by measuring certified reference materials and using them as standards. LIBS measurements were performed with a new mobile instrument Modì (Mobile Double pulse Instrument for LIBS Analysis) that use an innovative experimental set-up, based on the use of two suitably retarded laser pulses that greatly improves the potential of this technique for accurate quantitative analysis. XRF analyses were performed with a portable instrument ArtTAX that use a collimated X-Ray beam equipped with a fluxing system of helium gas on the detection path to the aim to detect the lighter elements with a good accuracy. LIBS results have shown that this technique is highly subjected to the sample chemical and physical characteristics.
Visualisation
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Influence of the artistic techniques on the visual appearance of complexions in art
Caroline Magnain, Mady Elias, Jean-Marc Frigerio
According to the epoch and place, the artists use the same pigments to paint the faces but change their techniques and the binders, which modify the visual appearances (color, gloss) of the works of art. Various techniques (encaustic, tempera, oil, synthetic binder) are investigated on model samples containing the same pigments but different binders and on a old painting. The influence of the techniques on the visual rendering is investigated experimentally. Goniophotometry and optical coherent tomography are used to determine the surface state, the gloss and the surface scattering. The spectrometry in the visible range allows to characterize the bulk scattering by determining the absorption and scattering coefficients of the pigments according to the binders. A particular oil technique, the art glaze is also studied on a real painting.
2.5D virtual reality visualisation of shearography strain data from a canvas painting
Advanced measurement techniques for the structural diagnostics of artwork are increasingly providing more complex data that needs to be conveyed to conservators in a meaningful way. Holography and speckle interferometry based sensors are commonly used for this application and of these shearography is quite suitable for measurements outside the optics laboratory, due to the stability of using a common path interferometer configuration. Shearography provides noncontact full-field displacement gradient data on surface and sub-surface defects in the form of phase maps. The display of this data in the form of wrapped phase maps is only suitable for experienced users. A further image processing step generates unwrapped phase maps, which in an engineering environment are generally colour coded for display. For artwork measurement applications, the colour variation of the painting itself is important reference for the conservator to locate defect locations. In this manuscript the displacement gradient data is presented as false height on the flat painting surface. A virtual reality viewer, freely downloadable from the internet, is used to display the data and allow the user to interact with it by rotating the object in virtual space. The effect is rather similar to viewing a raked light photograph, however with the advantage of remote or online viewing.
Application of graphically oriented programming to imaging of structure deterioration of historic glass by optical coherence tomography
Marcin Sylwestrzak, Ewa A. Kwiatkowska, Pawel Karaszkiewicz, et al.
Optical Coherence Tomography (OCT) is an interferometric method utilising light of low temporal coherence for noninvasive structural imaging of objects weakly absorbing and scattering light. In this contribution, using various examples of images of objects made of glass affected by the atmospheric corrosion and/or by crizzling, we demonstrate a software developed in our laboratory specifically for 3D OCT imaging of samples with a fine structure. For this task we employed the OpenGL platform (Open Graphics Library), an Application Programming Interface (API) for writing applications dedicated to interactive 3D computer graphics. In our application we have utilized texture rendering with a modulation of transparency and a colour as a function of elevation.
Application of optical techniques in documentation and identification of archaeological rests: the case study of the Roman bronze rest found in Lucentum
L. Granero, F. Diaz, R. Dominguez, et al.
In this paper it will be presented a case study of the optical technologies applicated to archaeology. This case study is centered in the main actions executed on an extraordinary rest appeared in the excavations of the Roman forum of Lucentum (Alicante, Spain) in 2005. This rest is a fragment of a bronze sculpture, and is catalogued as a Unicum (that is, a sample that presents some singular elements with no comparison with other samples, in this case of the Roman Art). That sample represents the only part that is conserved so far of that statue. This paper will explain briefly the main 3D digitizing systems and, after that, will focus in the process of identification and documentation of the rest. In particular, it will be widely described the 3D digitizing process of the rest and the post-processing of the information obtained on it, showing the main steps of the work and the results obtained, used subsequently in other processes.
Terahertz Imaging
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Terahertz metrology of tree rings for dendrochronology and cultural heritage applications
J. B. Jackson, J. Labaune, G. Mourou, et al.
Terahertz imaging will be presented as a novel method of nondestructively measuring otherwise inaccessible tree-rings for the purpose of dendrochronologically cross-dating cultural heritage artifacts. Wood specimens were measured using time-domain terahertz pulse reflectometry. Two-dimensional images of tree-rings were generated through analysis of both time- and frequency-domain terahertz signals, which changed proportionally to the variations in wood density. Terahertz pulse separation enabled wood specimens with at least two layers of coatings (primer and/or paint) to be measured and the terahertz images were quantitatively compared to the optical photographs of related, uncoated specimen. Tree-ring series and timelines were obtained for each terahertz image with respect to the source (reference) ring series. Short ring width blocks were aligned to the reference series and combined to create an extended timeline for each terahertz image. It was determined that while spatial resolution may be improved with analysis at high frequencies, the lower signal to noise reduces the precision of the ring measurement. Constructing longer timelines from ring blocks, significantly improves the overall quality of a match.
Terahertz imaging systems: a non-invasive technique for the analysis of paintings
Terahertz (THz) imaging is an emerging technique for non-invasive analysis. Since THz waves can penetrate opaque materials, various imaging systems that use THz waves have been developed to detect, for instance, concealed weapons, illegal drugs, and defects in polymer products. The absorption of THz waves by water is extremely strong, and hence, THz waves can be used to monitor the water content in various objects. THz imaging can be performed either by transmission or by reflection of THz waves. In particular, time domain reflection imaging uses THz pulses that propagate in specimens, and in this technique, pulses reflected from the surface and from the internal boundaries of the specimen are detected. In general, the internal structure is observed in crosssectional images obtained using micro-specimens taken from the work that is being analysed. On the other hand, in THz time-domain imaging, a map of the layer of interest can be easily obtained without collecting any samples. When realtime imaging is required, for example, in the investigation of the effect of a solvent or during the monitoring of water content, a THz camera can be used. The first application of THz time-domain imaging in the analysis of a historical tempera masterpiece was performed on the panel painting Polittico di Badia by Giotto, of the permanent collection of the Uffizi Gallery. The results of that analysis revealed that the work is composed of two layers of gypsum, with a canvas between these layers. In the paint layer, gold foils covered by paint were clearly observed, and the consumption or ageing of gold could be estimated by noting the amount of reflection. These results prove that THz imaging can yield useful information for conservation and restoration purposes.
Multi-sensor evaluation of a wooden panel painting using terahertz imaging and shearography
Roger M. Groves, Boris Pradarutti, Eleni Kouloumpi, et al.
Cultural heritage objects are increasingly being investigated using advanced non-destructive optical measurement techniques. Holographic and speckle interferometry based instrumentation allow dimensional measurement of objects at the tens of nanometer scale. For the structural diagnostics of artwork, double-exposure techniques are often used to locate defects, delaminations, voids and other structural features. Shearography is a speckle interferometry configuration that uses a close-to-common-path shearing interferometer configuration to give a direct sensitivity to displacement gradient at the object surface. This configuration is particularly useful for measurements outside the optical laboratory, as the stability requirements are much reduced compared with holography techniques. Terahertz imaging is a new category of sensor, used to investigate materials using electromagnetic radiation in the 0.1 to 10 THz frequency range. At these frequencies many materials become semi-transparent, so bulk structural diagnostics can be performed. Typically terahertz imaging is performed using a scanning pixel, or multi-pixel, sensor. In this manuscript shearography is first used to identify areas of interest of possible structural anomalies in the artwork. These regions of interest are then studied in more detail using the terahertz imaging instrument. Together the two instruments provide an analysis of both the surface and bulk structural features. The approach is demonstrated experimentally using a wooden panel painting.
OCT
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Absolute LIBS stratigraphy with optical coherence tomography
In this contribution preliminary studies on the application of Optical Coherence Tomography (OCT) to absolute depth calibration of Laser Induced Breakdown Spectroscopy (LIBS) data in application to revealing stratigraphy of easel paintings are presented. The procedure of in-situ monitoring of LIBS by means of OCT is described. Numerical method developed for precise extraction of the depth of the LIBS ablation crater is explained. Results obtained with model paintings are discussed.
Picosecond laser ablation system with process control by optical coherence tomography
In this contribution we describe an apparatus for precise laser ablation of delicate layers, like varnish on pictures. This specific case is very demanding. First of all any changes in colour of remaining varnish layer as well as underneath paint layers are unacceptable. This effect may be induced photochemically or thermically. In the first case strong absorption of the radiation used will eliminate its influence on underlying strata. The thermal effect is limited to so called heat affected zone (HAZ). In addition to colour change, a mechanical damage caused by overheating of the structure adjacent to ablated region should be considered also. All kinds of treads must be carefully eliminated in order to make laser ablation of varnish commonly accepted alternative to chemical and/or mechanical treatments [1]. Since the varnish ablation process is obviously irreversible its effective monitoring is very important to make it safe and trusted. As we showed previously [2-6] optical coherence tomography (OCT) originated from medicine diagnostic method for examination and imaging of cross-sections of weakly absorbing objects can be used for this task. OCT utilises infrared light for non-invasive structure examination and has been under consideration for the examining of objects of art since 2004 [7-10]. In this case the in-depth (axial) resolution is obtained by means of interference of light of high spatial (to ensure sensitivity) and very low temporal coherence (to ensure high axial resolution). In practice, IR sources of bandwidths from 25 to 150 nm are utilised. Resolutions obtained range from 15 down to 2 μm in the media of refracting index equal 1.5. In this contribution we expand application of OCT to space resolved determination of ablation rates, separately for every point of examined area. Such data help in better understanding of the ablation process, fine tuning the laser and finally permit increase of the safety of the ablation process.
Fourier domain optical coherence tomography for high-precision profilometry
A Fourier domain (FD) optical coherence tomography (OCT) system is shown to be capable of profilometry with two orders of magnitude better accuracy than the axial imaging resolution of the system. High precision OCT profilometry not only achieves similar accuracy as commercial white light interferometry based profilometers but is also capable of profilometry on complex subsurface structures with multiple interfaces of low reflectance. An accuracy of 55nm was achieved with a ThorLabs SROCT on a lab bench without special anti-vibration devices. This technique has the potential for a range of applications, such as high precision refractive index measurements and simultaneous dynamic monitoring of the interface structure of a drying varnish and the substrate.
Laser induced breakdown spectroscopy (LIBS) applied to stratigrafic elemental analysis and optical coherence tomography (OCT) to damage determination of cultural heritage Brazilian coins
Marcello M. Amaral, Marcus P. Raele, Anderson Z. de Freitas, et al.
This work presents a compositional characterization of 1939's Thousand "Réis" and 1945's One "Cruzeiro" Brazilian coins, forged on aluminum bronze alloy. The coins were irradiated by a Q-switched Nd:YAG laser with 4 ns pulse width and energy of 25mJ emitting at 1064nm reaching 3.1010Wcm-2 (assured condition for stoichiometric ablation), forming a plasma in a small fraction of the coin. Plasma emission was collected by an optical fiber system connected to an Echelle spectrometer. The capability of LIBS to remove small fraction of material was exploited and the coins were analyzed ablating layer by layer from patina to the bulk. The experimental conditions to assure reproductivity were determined by evaluation of three plasma paramethers: ionization temperature using Saha-Boltzmann plot, excitation temperature using Boltzmann plot, plasma density using Saha-Boltzmann plot and Stark broadening. The Calibration-Free LIBS technique was applied to both coins and the analytical determination of elemental composition was employed. In order to confirm the Edict Law elemental composition the results were corroborated by Neutron Activation Analysis (NAA). In both cases the results determined by CF-LIBS agreed to with the Edict Law and NAA determination. Besides the major components for the bronze alloy some other impurities were observed. Finally, in order to determine the coin damage made by the laser, the OCT (Optical Coherence Tomography) technique was used. After tree pulses of laser 54μg of coin material were removed reaching 120μm in depth.
Study of varnish layers with optical coherence tomography in both visible and infrared domains
Gaël Latour, Gaëlle Georges, Laure Siozade, et al.
Optical Coherence Tomography (OCT) is an attractive technique to study works of art because it allows non-destructive and contactless analysis. In the case of musical instruments, the study of wood finishes could give interesting information as the thicknesses of the layers, the number of layers and the presence of fillers. A time-domain full-field OCT, achieving high resolution, is used in both visible and near infrared ranges to characterize semi-transparent layers containing scattering particles as charged varnish layers. We present OCT measurements on wood varnished with different coatings. We show that the detection of pigment particles is dependent of the spectral range and that both spectral domains allow to reach micrometer-scale spatial resolutions.
3D
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Automated full-3D shape measurement of cultural heritage objects
Robert Sitnik, Maciej Karaszewski, Wojciech Zaluski, et al.
In this paper a fully automated 3D shape measurement system is presented. It consists of rotary stage for cultural heritage objects placement, vertical linear stage with mounted robot arm (with six degrees of freedom) and structured light measurement set-up mounted to its head. All these manipulation devices are automatically controlled by collision detection and next-best-view calculation modules. The goal of whole system is to automatically (without any user attention) and rapidly (from days and weeks to hours) measure whole object. Measurement head is automatically calibrated by the system and its possible working volume starts from centimeters and ends up to one meter. We present some measurement results with different working scenarios along with discussion about its possible applications.
3D synchrotron x-ray microtomography of paint samples
Ester S. B. Ferreira, Jaap J. Boon, Jerre van der Horst, et al.
Synchrotron based X-ray microtomography is a novel way to examine paint samples. The three dimensional distribution of pigment particles, binding media and their deterioration products as well as other features such as voids, are made visible in their original context through a computing environment without the need of physical sectioning. This avoids manipulation related artefacts. Experiments on paint chips (approximately 500 micron wide) were done on the TOMCAT beam line (TOmographic Microscopy and Coherent rAdiology experimenTs) at the Paul Scherrer Institute in Villigen, CH, using an x-ray energy of up to 40 keV. The x-ray absorption images are obtained at a resolution of 350 nm. The 3D dataset was analysed using the commercial 3D imaging software Avizo 5.1. Through this process, virtual sections of the paint sample can be obtained in any orientation. One of the topics currently under research are the ground layers of paintings by Cuno Amiet (1868- 1961), one of the most important Swiss painters of classical modernism, whose early work is currently the focus of research at the Swiss Institute for Art Research (SIK-ISEA). This technique gives access to information such as sample surface morphology, porosity, particle size distribution and even particle identification. In the case of calcium carbonate grounds for example, features like microfossils present in natural chalks, can be reconstructed and their species identified, thus potentially providing information towards the mineral origin. One further elegant feature of this technique is that a target section can be selected within the 3D data set, before exposing it to obtain chemical data. Virtual sections can then be compared with cross sections of the same samples made in the traditional way.
NIR confocal microscopy for painting diagnostics
C. Daffara, R. Fontana, L. Pezzati
We designed and built a simple fiber-optic confocal laser-scanning interference microscope, operating in the near infrared (NIR), for the analysis of paintings. We applied this instrument to the non-invasive optical sectioning of the paint layers. The device was tested on both laboratory samples and ancient paintings. The preliminary results show that optical sections obtained by NIR confocal microscopy are comparable to those recorded with well known optical coherence tomography and a few examples of application are presented.
Comparison of carved panels from two Irish high crosses using laser scans
Thierry Daubos, Dáibhí Ó Cróinín
We present the results we obtained in comparing several carved panels from two high crosses. In this study, which was carried out as part of the RTE Cork TV program "Secrets of the Stones", we compared three panels of the Cross of the Scriptures from the Clonmacnois monastic site, Co. Offaly with similar panels from the Cross of Durrow, located in the grounds of St Columba monastery, Co. Offaly. The purpose of the study was to decide whether these high crosses, which both date back to the ninth century, could have been carved by the same Celtic artist. The Cross of the Scriptures was scanned in August 2008 using our Polhemus FastSCAN handheld laser scanner, while the Cross of Durrow was surveyed in May 2008 by the Germany based, ArcTron 3D company, commissioned by the Offaly County Council. Using the data from the 3D scans, details of each panel were enhanced using a wavelet filtering technique and a false colour image of the depth field was computed for each panel. These images were then used as textures and applied back onto the 3D models. This process allowed for expert historians to later on evaluate, by looking and manipulating the textured 3D models, the hypothesis that the panels were carved by the same person.
Dual scale structural health monitoring system combining FBG sensors and laser scanning
Hugo F. Lima, M. Fátima Domingues, Rogério N. Nogueira, et al.
This work reports a case study of a structural health monitoring (SHM) system combining large and micro scale measurements installed in a 16th Century Church in Aveiro. This dual scale SHM system relies on a network of 24 fibre Bragg grating (FBG) sensors to perform micro scale, high resolution displacement and temperature measurements in several key points of the structure, while the large scale measurements are ensured by a scanning laser range finder. The results demonstrate that the developed systems allow adequate monitoring of the evolution of deformation in buildings, in different scales, keeping the visual impact in the structure reduced to a minimum and contributing for the implementation of best practices for rehabilitation of historic and cultural heritage.
Poster Session
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Comparative evaluation of ultrafast laser beam interaction with the silvering in late Roman coins
A. A. Serafetinides, E. Drakaki, E. Fabrikesi, et al.
This work investigates the influence of the pulse duration and the wavelength on the laser cleaning of thin silver plating layers found in late Roman coins. Comparative cleaning tests were performed using Nd:YAG (1064 nm and 532 nm - 6 ns), GaAlAs diode (780 nm - 90 ps) and Ti-Sapphire regenerative amplifier (800 nm - 100 fs) laser systems. The cleaning results on the plated areas were characterised by high resolution optical microscopy, SEM-EDX, XRF and micro-profilometry.
LIBS identification of pigments from Aula Leopoldina vault
Aula Leopoldina is the most representative, baroque hall in Wroclaw University. In 2008, LIBS measurements of paintings layers of Aula vault were done. LIBS spectra permitted identification of mineral pigments used for specific colors of painting layers. This identification could not be unambiguous in each case since simultaneous occurrence of elements that could be components of different pigments of the same color was observed in some samples. For example, in some red samples the presence of aluminum and iron was stated, and hence red ochre or Mars red could be used as a pigment. In other samples the cinnabar can be additionally responsible for red color. Similar problems were observed in case of blue pigments, where existence of copper may show that azurite was used, but the presence of aluminum, sodium, silicon and iron can point to application of ultramarine, Egyptian or Prussian blues. The greatest difficulties occurred during identification of white pigments. Because of presence of barium, zinc, lead and titanium, the potential pigments might be lithopone, barite, zinc white, lead white or titanium white. Final choice of the pigment is determined by the time of last renovation and this points out that the zinc white was used.
Analysis of the European lacquer technique and technology of polychromed wooden decoration of Chinese room in Wilanow Palace in Warsaw
Irmina Zadrozna, Anna Guzowska, Elzbieta Jezewska
A well preserved wooden paneling decoration of one of the rooms adhering to the King's Jan III bedroom in Wilanow Palace is a unique example of European lacquerwork attributed to famous 18th century craft workshop of Martin Schnell. This decorative technique is a method of applying many layers of clear or colored composition of resins available in Europe to especially prepared ground layer. The paper summarizes the results of original painting materials identification as well as original and late layers stratigraphy. Under certainly not original parts of polychromy there were other colors found. It has been discovered also that some parts of the wooden paneling was removed and replaced with copies painted in a different technique. The 3D scanner and produced orthophotoplans allowed full documentation of the state of preservation of the whole room. The paint samples of which stratigraphic cross-sections were made have been analysed with SEM-EDS technique and ultraviolet fluorescence microscopy. Application of the most advanced analysis techniques like Gas Chromatography (GC/MS) and Fourier-Transform infrared spectroscopy (FTIR) allowed the most exact identification of binding media.
Conservation of wooden art works and laser cleaning
A. Koss, M. Lubryczynska, J. Czernichowska, et al.
Laser cleaning technique has been thoroughly compared to traditional chemical and mechanical procedures in the several case studies of wooden artworks, particularly when conventional cleaning tests showed that none of the methods known to experienced restorers met all the requirements. Laser cleaning tool, included into conservation projects, appeared to be very successful in the removal of old overpaintings, dirt clusters in deep artworks fractures and hollows as well as removal of sootiness formed by mixture of soot, wax, stearin and dust from coloured polychrome. Moreover, laser cleaning appeared to be much faster and safer for original wooden artwork substrates, especially in deeper fragments of sculptured areas. Four case studies of different historical objects with wood as an original substrate material will be presented. In all cases, conservation treatments followed detailed structural stratigraphy of layers and identification of materials. For comparison, paper includes also some citations from authors earlier published works1-2.
Set of advanced laser cleaning heads and systems
Paper presents three developments of laser systems aimed at more safe and efficient cleaning of paper and parchment, paintings and metal artworks. Short introduction and scope of our work are included in the first paragraph. In the following sections are presented in details: - picosecond, diode pumped Nd:YAG laser system with computer controlled manipulation table and proposed "online" cleaning diagnostic systems for cleaning of paper, parchment and paintings, - ReNOVALasErb laser cleaning system (2.94 μm) with narrowed width of output pulses for cleaning of paintings, - generator-amplifier Nd:YAG laser configuration aimed at temporal and amplitude shaping of output Q-switched laser pulses for cleaning of metal artworks.
In-depth assessment of modifications induced during the laser cleaning of modern paintings
Alexandros Selimis, Panagiota Vounisiou, George J. Tserevelakis, et al.
A critical challenge for the broader implementation of laser cleaning interventions in modern paintings is the assessment of the extent of any photochemical or structural modifications induced in the original substrate following laser irradiation. For this reason, we investigate several polymeric materials (PMMA, Paraloid B72) doped with aromatic photosensitisers (PhenI, POPOP) of known photochemistry, coated with uniform layers of acrylics of different thicknesses to simulate real case scenarios. Following laser irradiation, a variety of spectroscopic techniques LIF, MPEF are employed for the in depth monitoring of any photochemical and structural modifications induced in the bulk material.
Imaging data integration for painting diagnostics
C. Daffara, D. Ambrosini, R. Di Biase, et al.
In the field of art conservation non-invasive techniques based on imaging in different spectral regions are widely used for investigation of paintings. Using radiation beyond the visible range, different characteristics of the inspected artwork may be revealed according to the bandwidth acquired. Beyond the traditional diagnostic methods, such as reflectography, thermography, selective multi-spectral analysis in the near-infrared region has been recently demonstrated to be a promising tool for investigating pictorial layers. In this work we present the results of a multidisciplinary collaboration among two research institutes and the Accademia Galleries of Venice concerning an integrated approach for multi-view and multi-spectral imaging data analysis for the diagnostics of paintings. In order to perform this integrated analysis, a graphical user interface with options such as image adjustment, overlaying and transparency variation was designed. The effectiveness of this integrated approach is recognized by the operators in the field of conservation that may thus have at their disposal the complete set of information spanning the different characteristics of the object under investigation. Data integration provides a multi-layered and multi-spectral representation of the painting that yields a comprehensive analysis, confirms the anomalies individuation and reduces the ambiguity of information coming from a single diagnostic method.
X-ray CT imaging as a scientific tool to study the capillary water absorption in sedimentary rocks used in cultural heritages
M. F. Alberghina, R. Barraco, M. Brai, et al.
This paper proposes the X-Ray CT imaging as appropriate tool for investigating the capillary water absorption in sedimentary rocks. This technique, in fact, provides information useful for deeping the knowledge about of the porosity and the kinetics of the water capillary absorption in porous materials. The possibility to improve in non invasive manner, the understanding of this phenomenon, constitutes a fundamental aspect to take actions in the restoration and conservation of lapideous artifact and monuments from cultural heritages. The investigated sedimentary rocks come from different Sicilian quarries and were used for the building of the Greek temples in the archaeological areas of Agrigento, Selinunte and in the baroque monuments of the Val di Noto area. The image acquisition was carried out at different times after contact with water. The wetting front progression along the height of the sample was evaluated on the basis of the estimated CT attenuation value maps. An average of the CT attenuation values measured by the ROI (Region of Interest) was used to evaluate the mean height of the wetting front, with different CT scans at fixed time intervals after sample wetting, in order to describe the dynamic behaviour of the imbibition process. CT imaging results have shown that the water absorption is highly subject to the sample porous morphology.
Noninvasive conoscopic holography-based device for artworks surface acquisition
P. Carcagnì, E. Cavallo, A. Della Patria, et al.
Surface topography is very important for many applications. Today the most used techniques on artworks and stone artifacts require long acquisition times and invasive interventions. For this reason, here a non-contact device improved in portability is described. It can acquire wide areas in short times, so it is suitable for topography reconstruction with spatial resolution of some tens of micrometers. The starting point is a commercial conoscopic probe, the Optimet Conoline, that is able to reconstruct the depth profile of a surface line probed by a built-in laser. Its accuracy and acquisition speed are as high as to return wide measured areas in short times; its resolution permits fine details reproduction. Low interference with the artwork, high portability and low response to environmental noise are the ingredients for the instrumental setup.