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The Eye of the Medusa - XRF Imaging Reveals Unknown Traces of Antique Polychromy
Abstract
The colorful decoration of statues and buildings in antique times is commonly described by the term Antique Polychromy. It is well known among scholars but less so in the interested public and its exact form is subject of ongoing research. In this paper we discuss results obtained from the Frieze of the Siphnian Treasury from the Sanctuary of Delphi (Greece). We will present the first applica-tion of a mobile instrument for macro-XRF imaging in the investigation of the Antique Polychromy and show that it allows to find significant traces not visible to the naked eye and not detectable by XRF spot measurements or any other mobile, non-invasive method. These findings allow for a partial reconstruction of the polychromy. Further, we present a novel approach to correctly interpret artifacts resulting from changes of the detection geometry in the investigation of complexly shaped samples by XRF imag-ing. This approach is based on the 3D surface model acquired by photogrammetry and fundamental parameter calculations.
... This renders the identification of the remnants of paint covering the surface close to guess work. In the original study, the problem was addressed by the fundamental parameter simulation of the investigation based on a photogrammetric 3D model of the Gorgoneion, but following the surface with a 3D instrument would have allowed for the acquisition of clear data to begin with [17]. . XRF measurement geometries on a curved 3D sample with three layers. ...
... This renders the identification of the remnants of paint covering the surface close to guess work. In the original study, the problem was addressed by the fundamental parameter simulation of the investigation based on a photogrammetric 3D model of the Gorgoneion, but following the surface with a 3D instrument would have allowed for the acquisition of clear data to begin with [17]. One problem that remains unaddressed in the MA-XRF imaging of 3D objects is that the footprint of the primary beam on the surface changes with the detection geometry due to surface tilt, and that all X-ray tube-based beams are ultimately divergent. ...
... The image was acquired with a horizontal step size of 0.5 mm, a vertical step size of 1 mm and a dwell time of 250 ms. Adapted from Alfeld et al.[17]. ...
The acquisition of elemental and chemical distribution images on the surface of cultural heritage objects has provided us new insights into our past. The techniques commonly employed, such as macroscopic X-ray fluorescence imaging (MA-XRF), in general require pointwise or whisk-broom scanning of an object under constant measurement geometry for optimal results. Most scanners in this field use stacked linear motorized stages, which are a proven solution for 2D sample positioning. Instead of these serial systems, we propose the use of a parallel cable robot to position the measurement head relative to the object investigated. In this article, we illustrate the significance of the issue and present our own cable robot prototype and test its capabilities, but also discuss the current shortcomings of the concept. With this, we demonstrate the potential of cable robots as platforms for MA-XRF and similar imaging techniques.
... Lastly, systematic studies have been conducted on the remains of paint on marble sculptures, but few analytical publications contain a description of the analytical methodology (Brons et al. 2020;Magrini et al. 2019;Bracci et al. 2020;Alfeld et al. 2017;Aggelakopoulou and Bakolas 2022;Abbe and Şare Ağtürk 2019). The commonly defined noninvasive standard protocol involves the use of multispectral imaging and video microscopy coupled with non-invasive punctual spectroscopies (Raman, XRF, FTIR) corresponding to the areas where the remains of colour are observed (Østergaard 2018). ...
... The commonly defined noninvasive standard protocol involves the use of multispectral imaging and video microscopy coupled with non-invasive punctual spectroscopies (Raman, XRF, FTIR) corresponding to the areas where the remains of colour are observed (Østergaard 2018). However, as has been demonstrated in an earlier publication (Alfeld et al. 2017), spot analysis makes it difficult to match visual observation with physico-chemical data. Consequently, contaminations from soil or from the iron elements that connect the different parts of the marble statues can be misinterpreted as traces of pigments. ...
... The position of the X-ray tube, detector and collimator was fixed by a 3D-printed plastic holder. The instrument was previously described elsewhere (Alfeld et al 2017). 18 scans were carried out on the objects discussed in this article. ...
If ancient written sources and the visual analysis of polychromies have recently revealed the complexity of the technique of painting on statues and their frequent restoration, the non-invasive punctual chemical analyses carried out do not allow one to access the chemical composition of the different paint layers. This paper presents the analysis of three statues from Roman Africa discussing the results obtained from this understudied territory and chronology. By combining visual observation (VIS, UVL), video microscopy and MA-XRF imaging, we propose here a non-invasive protocol to determine the chemical composition of the different paint layers. This allows one to unveil the complexity of the ‘know-how’ of a sculpture painter and sheds light on the evolution of the original appearance of the statues.
... MA-XRF has been used for the investigation of the distribution of ancient pigments at synchrotron radiation sources [12][13][14] and one mobile application has been reported [15]. Mobile hyperspectral reflectance imaging has not yet been applied to the study of ancient pigment use. ...
... In this publication we describe the investigation of ancient polychromy on the Frieze of the Siphnian Treasury (6th century BC) in the Delphi Archaeological Museum (Greece), described in detail in Section 2.1. In a previous study on the same object we showed the value of MA-XRF to reveal traces of pigments hidden under soil encrustation on the head of Medusa on the shield of Achilleus (shown in the right of the photograph in Fig. 4) and used the combination of a 3D model obtained by photogrammetry and fundamental parameter calculations to address the complex shape of the object [15]. ...
... Spot measurements were done with 300 s/ spot. The instrument is virtually identical to the one used previously [15] with the exception of the changed detection angle and shown in Fig. 1. ...
Of the once colourful decoration of antique Greek statues only few traces remain today. But these allow one to reconstruct part of the polychromy, based on visual and microscopic inspection and spot analysis with spectroscopic methods. For the first time we used mobile hyperspectral reflectance imaging in the visible and near infrared range and scanning macro XRF imaging for the investigation of remnants of antique polychromy on a stationary object. With this method of analysis we were able to reveal previously unknown traces of ancient paint on the Frieze of the Siphnian Treasury (around 525 BCE). This illustrates the capabilities of this techniques to obtain new insights in a well-described and investigated object. Further, we gained insight into the painting technique, involving an earth based preparation layer. Finally, we present an alternative way to the treatment of the hyperspectral reflectance data in order to obtain easily readable pigment distribution images in case of heterogeneous illumination.
... This problem was addressed by using fundamental parameter calculations in combination with photogrammetry, i.e., the calculation of an object's 3D shape based on series of photographs. Results are shown in Fig. 6 [122]. ...
... Similar, as discussed above, fundamental parameter based calculations were used, not to correct for differences in stratigraphy but in object shape and thus measurement geometry of painted 6th century BC marble statues, based on 3D models obtained with photogrammetry [122]. ...
... The distribution images allow identifying the pigments clearly as remnants of the original polychromy, which remained hidden under soil encrustations and went undetected during previous investigations. Adapted from[122]. ...
This paper provides an overview over the application of scanning macro-XRF with mobile instruments for the investigation of historical paintings. The method is compared to synchrotron based macro-XRF imaging and Neutron Activation Auto-Radiography. Full-Field XRF imaging instruments, a potential future alternative to scanning macro-XRF, and confocal XRF, providing complementary depth profiles and developing into a 3D imaging technique itself, are described with the focus on investigations of historical paintings. Recent developments of X-ray radiography are presented and the investigation of cultural heritage objects other than paintings by MA-XRF is summarized. In parallel to XRF, hyperspectral imaging in the visible and range has developed into a technique with comparable capabilities, providing insight in chemical compounds, where XRF imaging identifies the distribution of elements. Due to the complementary nature of these techniques the latter is summarized. Further, progress and state of the art in data evaluation for spectroscopic imaging is discussed. In general it could be observed that technical capabilities in MA-XRF and hyperspectral imaging have reached a plateau and that with the availability of commercial instruments the focus of recent studies has shifted from the development of methods to applications of the instruments. Further, that while simple instruments are easily available with medium budgets only few groups have high-end instrumentation available, bought or in-house built.
... They also allow the demonstrative visualization of overpainted and altered pictorial details [22,23]. For example, MA-XRF has also been used in combination with hyperspectral imaging for the investigation of a funerary Greco-Roman painted portrait dating from the 2nd century AD Egypt at the National Gallery in Washington, D.C. [24] or for the identification of the remnants of colours present on marble in Delphi (Greece) [25,26]. The possibility of combining both methods with unsupervised machine learning (t-Stochastic Neighbour Embedding) has been demonstrated on Egyptian paintings [27]. ...
... University, Belgium). These instruments described respectively in [26] and in [29,30] are dedicated specifically for the on-site non-invasive investigation of heritage artifacts: this specification led to the production of lightweight devices, transportable in normal check-in luggage, that can be installed in narrow spaces and on uneven ground, while being battery operated if needed. ...
The material study of ancient Egyptian paintings began with the advent of Egyptology during the 19th century. By the 1930s, a lot had already been sampled and described. The limited palette for example has been analysed from actual painted surfaces but also from pigments and painting tools retrieved on site. However, most of these studies took place in museums while the painted surfaces, preserved in funerary chapels and temples, remained somewhat estranged from this primary physical understanding. The artistic process has been also reconstructed, mainly from the information presented by unfinished monuments, showing surfaces at different stages of completion. A lot of this modern and theoretical reconstruction is, however, based on the usual archaeological guessing game that aims at filling the remaining blanks. Our interdisciplinary project has decided to experiment on-site with state-of-the-art portable analysis tools, avoiding any physical sampling, to see if our knowledge of the work of the ancient Egyptian painters and draughtsmen could be taken at a further stage, while based on physical quantification that could be seen as a stronger and more reliable foundation for a redefined scientific hypothesis. The use of XRF mapping has, for instance, been applied to a known case of correction by surface repaint, something that is supposedly rare in the ancient Egyptian formal artistic process, while another fully unexpected one was discovered during the analytic exploration of a royal representation. In both cases, the precise and readable imaging of the physical composition of the painted surface offers a renewed visual approach based of chemistry, that can be shared through a multi- and interdisciplinary approach. However, this also leads to a more complex description of pigment mixtures that could have multiple meanings, where the practical often leads towards the symbolic, and from there hopefully to a renewed definition of the use of colours in complex sets of ancient Egyptian representations. At this stage, though the progress in this on-site material assessment of ancient works of art definitely means astonishing progress, one humbly has to face the fact that these ancient treasures shall still retain part of their defining mysteries.
... The continuous optimization of MA-XRF spectrometers has allowed the creation of elemental images over extended areas of painted artworks (Romano et al., 2017;Trentelman, 2017;Križnar et al., 2018), whereas most recently been applied for the investigation of ancient painting and polychromy. (Alfeld et al., 2017(Alfeld et al., , 2018bKantarelou et al., 2016;Alfeld et al., 2018a) Macro-XRF imaging and mobile hyperspectral reflectance were applied on the marble frieze of the Siphnian Treasury in the Sanctuary of Delphi (Greece), allowing the detection of traces of pigments invisible to the naked eye and therefore never previously recorded. The benefits of performing MA-XRF on painted stationary objects with a mobile instrumentation have also been made evident in the investigation of the Etruscan wall-paintings of the Banditaccia Necropolis, near Cerveteri (Alfeld et al., 2018a) and on the Archaic statue of Phrasikleia, (Kantarelou et al., 2016) while a first impressive application of a multimodal chemical imaging, including MA-XRF analysis was presented for the characterization of painting materials on a Greco-Roman portrait from Fayum, Egypt. ...
... In the examined areas, relatively elevated traces of bromine (Br) were detected, with respect to the substrate, suggesting the use of the organic colorant Murex purple ( Fig. 8a and b), a hypothesis which is in accordance with the results of HPLC analysis on purple colored samples from Hall 64. (Alfeld et al., 2017) The spectra in Fig. 8a and b were acquired by using the Ni/Fe/Ti combined filter in the exciting X-ray beam path, which improved considerably the peakto background ratio in the energy region that the Br-Kα peak is expected to be recorded. ...
The wall painting fragments from the Mycenaean “Palace of Nestor” at Pylos, are characterized by their high artistic quality, their unusual iconographic variety and the use of tempera and secco painting techniques. Systematic in-situ XRF analyses combined with the results of other portable and laboratory analytical techniques have already revealed a rich gamut of inorganic pigments with respect to the common Aegean “palette”, including different white and black pigments, iron based ochres ranging from dark brown to orange and pinkish hues, manganese based umbers, natural copper based greens, goethite, Egyptian blue and organic purple dyes. Macroscopic X-ray Fluorescence (MA-XRF) imaging, although well-established for non-invasive analysis of historical or contemporary painted artworks has hitherto been applied in a few cases only regarding the study of ancient polychromy. The purpose of applying in-situ MA-XRF imaging on selected wall painting fragments from the Palace of Pylos was to evaluate the capabilities of this technique in identifying the composition of pigments and their spatial distribution within heavily deteriorated pictorial layers, and in revealing iconographic information invisible to the naked eye. The results of MA-XRF imaging allowed us to critically re-consider previous artistic reconstructions, providing significant evidence on the painting techniques and materials used by Late Bronze Age painters.
... However, the investigated objects are rather reliefs and not full 3D shapes. Other solutions worth noting for elemental imaging of non-flat objects are also those based on photogrammetric modelling combined with point XRF analysis 38,39 or computer tomography combined with full-field imaging 40 . ...
This article explores the performance and capabilities of a custom-developed full-field XRF imaging spectrometer operating at limited energy resolution (1.1 keV FWHM at 5.9 keV) for elemental mapping of three-dimensional (3D) objects. The measurements performed involved two, different in spatial depth, historical artworks from the collection of the National Museum in Krakow. The first is an object of low significance, used in principle as a phantom, while the second is an actual cultural heritage object. The resulting maps of elemental distributions are presented, along with detailed descriptions and a discussion on pigment identification. Finally, specific features, analysis artefacts, as well as benefits and limitations of the system are discussed. The results obtained for the investigated objects confirm the capability of the developed instrument for XRF elemental imaging of 3D objects and its usefulness in the field of cultural heritage research.
... From each spot/area of interest, two distinct spectra were collected; the first spectrum was collected with the instrument operating in a 15 kV and 70 µA mode (no filter) while the second was obtained using a 40 kV and 100 µA setup (with a composite Ti/Al filter). In both cases, spectra were collected through a 3 mm collimator for 10 s [20,21]. Subsequently, spectra were processed using the Artax software (Bruker). ...
The Gigantomachy depicted on the west pediment of the Late Archaic temple of Apollo at Delphi marks a significant milestone in early Greek architectural sculpture. Crafted from porous stone and enhanced with plaster and paint, the surviving fragments differ markedly from the marble figures of the east pediment of the same temple. Among the preserved figures of the Gigantomachy are a standing male figure, possibly representing Apollo or Dionysos, a warrior female identified as Athena, and a recumbent male, likely symbolizing the Giant Enkelados. This study aims to investigate the polychromy of the west pediment through a thorough investigation of the remnants of the original decoration. The adopted methodology includes exclusively non-destructive techniques and advanced imaging methods, such as portable X-ray fluorescence spectrometry, visible-induced luminescence (VIL), and 3D microscope observation. Analytical results confirmed the presence of extensive traces of once-vibrant colors on the plaster’s surface, which were often invisible to the naked eye. Specifically, our data support the employment of pigments like Egyptian blue, cinnabar, ochre-based reds and yellows, as well as copper-based green. Notably, these pigments were applied over a white calcium-rich layer, which served as a primer for the porous stone. Ongoing research on the Gigantomachy promises to deepen our understanding of color usage and painting techniques in Archaic Greek art.
... In the theoretical calculation aspect, the sample surface relief angle was introduced to correct the angles of incident X-rays and emitted XRF. By solving the fundamental parameter equations for known sample components, the surface relief angles were calculated to correct the influence of the surface effect on the analysis results [18], [19]. Another method was to assume that a major matrix element of the sample was expected to be uniformly distributed, such as Ca for marble. ...
In MA-XRF imaging devices, a larger beam size leads to worse spatial resolution, and the surface topography can produce shadow patterns in the image that hinder its analysis. In this study, a portable MA-XRF imaging device is constructed, and the performance of the device is measured. Three image reconstruction algorithms are introduced, including compressive sensing, L0-regularized intensity and gradient prior, and blind deconvolution, to compare the image reconstruction of the USAF 1951 resolution test target. The results show that the blind deconvolution algorithm outperformed the other two methods, achieving up to a 35% improvement in spatial resolution, a 24.2% enhancement in image signal-to-noise ratio, and an optimal spatial resolution of 0.36 mm (1.39 lp/mm). An intensity theoretical calculation model of XRF based on the sample surface topography is established. The Copper map of a "5 Jiao" coin is corrected and the mean deviation decreased by 5.7%. Finally, a piece of lapis lazuli is analyzed, and the quality of the element maps of K, Ca, and Sr is improved by the surface topography correction and image reconstruction, with spatial resolutions increasing by 36.1%, 34.4%, and 33.5%, respectively. The research in this paper demonstrates that the MA-XRF imaging device based on spatial resolution optimization and surface topography correction algorithms has promising applications.
... Portable single-point X-ray fluorescence system, developed inhouse and entitled scanX [ 23 ], is composed of a Pd anode transmission tube (Moxtek MAGNUM, Orem, Utah) and a Amptek SDD (active area of 70 mm ²) mounted on a manual translation stage. The instrument was operated at 30 kV and 0,05 mA, with a dwell time of 180 ms per point. ...
The material study of fragile graphic artworks requires adapted analytical methodologies to extract representative information without resorting to sampling. In this paper, a multimodal approach combining non-invasive techniques was developed to specifically characterize the artistic materials used (paper, pigment/filler and binder) in 3 pastel portraits by the famous French pastellist, Maurice Quentin de La Tour (1704–1788). The combination of elemental analyses using X-ray fluorescence and reflectance spectroscopies covering the entire energy range from 25,000 to 400 cm−1, has provided new insights into the nature and state of conservation of the paper support, as well as the composition and application of the pastel materials. Bridging technical art history, conservation science and analytical chemistry, this research offers a unique perspective on the choice of materials of the renown pastellist, and sheds new light on an artistic technique understudied until now.
... The motorized stage was fixed to a 3-axis manual rotation stage mounted on a photographic tripod. The instrument has been previously described elsewhere [22]. The central area was investigated using a step size of 1 mm and a dwell time per pixel 0.2 s. ...
The Transfiguration by Giovanni Bellini in the Museo di Capodimonte (Naples) is an iconic image of a transcendental event at the heart of the Christian religion. Using non-destructive chemical imaging, and focusing on the central image of the transfigured Christ we have studied by what means and with what materials the artist represented this divine event. The results showed what is to date the earliest use of the pigment stibnite. The techniques employed demonstrate both continuity with Bellini’s earliest works (such as the combination of the use of shell-gold and organic, tinted layers), but also his knowledge of Netherlandish painting. This research has furthered our understanding of how he achieved the luminosity so characteristic of his translation of the divine into the materiality of paint.
... Polychromy was extensively used on stone sculptures [2][3][4], architectural elements [5,6], and on terracotta figurines [7][8][9] as a constituent component of three-dimensional artworks due to the symbolic, communicative, and aesthetic use of color [10]. After the Second World War, the debate about the polychromy of ancient sculptures attracted scholars from many disciplines, whose research has been devoted to the reconstruction of the original appearance of artefacts through investigation of their surfaces and the analysis of pigment remains since then [3,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Advances in technical photography strongly enhanced out capacity to visualize residual traces of pigments, becoming crucial in creating three-dimensional, physical reconstructions of painted sculptures [1,12,13]. ...
Polychromy in Ancient Greek Sculpture was the subject of the exhibition Chroma: Ancient Greek Sculpture in Color, held at The Metropolitan Museum of Art (The Met), New York, in 2022–2023. On this occasion, a multidisciplinary project involving The Met’s Departments of Greek and Roman Art, Objects Conservation, Imaging, Scientific Research, and colleagues from the Liebieghaus Polychromy Research Project in Frankfurt, Germany, was carried out to study an Attic funerary monument. The color decoration of the sphinx was reconstructed by combining non-invasive and minimally invasive techniques that provided information about surviving and lost pigments, original design, and painting technique. Results of multiband imaging, digital microscopy, and X-ray fluorescence spectroscopy guided the removal of minute samples from selected areas for examination by Raman spectroscopy and scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy, to shed light on the pigments and paint stratigraphy. The color palette included two varieties of blue, Egyptian blue and azurite, a carbon-based black pigment, two reds, cinnabar and red ocher, and yellow ocher, all painted directly over the marble without a preparation layer. The scientific findings informed the physical reconstruction of the sphinx made by archaeologists from the Liebieghaus Polychromy Research Project, featured in the exhibition.
... The technique is relatively fast; the acquisition time naturally depends on the dimensions of the area of analysis and the dimensions and characteristics of the instrument employed. Numerous types of equipment are available nowadays, ranging from small and easy-to-transport instruments customized for the analysis of areas of only a few cm 2 [2,3] to massive scanners allowing large areas to be analysed in a reasonably short acquisition time [4][5][6]. ...
At present, macro X-ray fluorescence (MA-XRF) is one of the most essential analytical methods exploited by heritage science. By providing spatial distribution elemental maps, not only does it allow for material characterisation but also to understand, or at least to have a likely idea of, the production techniques of an analysed object. INFN-CHNet, the Cultural Heritage Network of the Italian National Institute of Nuclear Physics, designed and developed a MA-XRF scanner aiming to be a lightweight, easy to transport piece of equipment for use in in situ measurements. In this study, the INFN-CHNet MA-XRF scanner was employed for the analysis of a painting by the Flemish artist Rogier van der Weyden. The painting belongs to the collection of the Uffizi gallery in Florence and was analysed during conservation treatments at the Opificio delle Pietre Dure, one of the main conservation centres in Italy. The research aims were to characterise the materials employed by the artist and to possibly understand his painting technique. Although MA-XRF alone cannot provide a comprehensive characterisation, it nonetheless proved to be an invaluable tool for providing an initial overview or hypothesis of the painting materials and techniques used.
... However, XRF imaging is mostly restricted to "2D objects", as the measurement head is usually moved in a plane parallel to the studied surface. We can cite as examples application to historical paintings, which have the great advantage to present a flat surface [4,5], stained-glass windows, illuminated manuscripts, antique polychromy [6,7] Several authors propose also to combine elemental and vibrational imaging techniques to achieve a more complete chemical description of the artwork surfaces [8][9][10][11]. However, these spectroscopic techniques may fail to distinguish materials with the same elemental/molecular composition but different crystalline structures. ...
Two polychrome sculptures from the late Middle Age were investigated by means of non-invasive techniques with the aim of characterizing sophisticated relief decoration named "applied brocade". Here, we have used portable instrumentation solely in order to perform X-ray powder diffraction and fluorescence measurements at the surface of the sculptures. The results show a reliable localisation and identification of the different materials making up an applied brocade: a filler material, a tin-based foil and a gilding, even in the case of a largely overpainted sculpture. More particularly, a direct identification of the organic material used for the filler as natural beeswax is proposed. Differences between the two investigated art-works have also been identified: (i) in the structure of the calcium sulphate preparation layers (one or double layer of gesso) (ii) in the presence or absence of a priming paint layer under decors (iii) in the choice of the material used to make the gilding: pure gold or probable zwischgold. The characterization of the degradation of this type of decorations was also assessed, namely romarchite (SnO) and cassiterite (SnO 2) were identified and their relative proportion estimated.
... However, artists purposefully create paintings with topographical surface to provide a level of plasticity and depth. This is particularly interesting for painted marbles from Roman or Greek antiquity [2,7] where correction for variation in the surface was made in post processing. However, not all image distortion is recoverable and may more easily be avoided when capturing an image. ...
Cultural heritage science envisages understanding of methods and techniques used by past painters and sculptors in creating their masterpieces of art. Existing devices for in situ and non-destructive, automated scanning are large and bulky and built around the assumption of a perfectly planar surface. We are developing a lightweight, portable robot for scanning of paintings, marbles, or statues while explicitly allowing for their out-of-plane surface. This paper presents the kinematic design and analysis of the wrench-feasible workspace of a cable-driven parallel robot capable of positioning an imaging device with three translational and two rotational degrees of freedom. At the end stand geometric parameters optimized for the application requirements allowing for pan and tilt of 70 each in total, making scanning of the spatial surface of art objects possible.
... 10 Chemical imaging methods can be divided into two distinct categories of elemental or molecular species information. On the one hand, there are elemental mapping/imaging techniques 11 such as X-ray fluorescence (XRF), 12 laser ablation (LA)-inductively coupled plasma-mass spectrometry (ICP-MS), 13 and glow discharge (GD) plasmas. 14 These techniques provide information on how certain elements are distributed across and within a structure. ...
The spatial distributions of elemental and molecular species are vital pieces of information for a broad number of applications such as material development and bio/environmental analysis. There is currently no single analytical method that can simultaneously acquire elemental, molecular, and spatial information from a single sample. This paper presents the coupling of an NWR213 laser ablation (LA) system to the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma for combined atomic and molecular (CAM) analysis. The work demonstrates a fundamental balance that must be considered between the extent of fragmentation of molecules and ionization of atoms for CAM analysis. Detailed studies showed that the interelectrode gap to be a critical parameter for controlling the ionization efficiency of atomic and molecular species. Utilizing Design-of-Experiment (DoE) procedures, the discharge current was also found to be a significant parameter to control. Elemental lead, caffeine, and simultaneous lead and caffeine analysis via LA-LS-APGD-MS was made possible through improved understanding of the influence of plasma parameters on the product mass spectra of laser-ablated particles. Finally, a chemical map of elemental lead and molecular caffeine, from lead nitrate and caffeine residues, was generated, demonstrating the comprehensive mapping capabilities of LA-LS-APGD-MS. The practical relevance of the capabilities is demonstrated by mapping glutamic acid from a cryosectioned chicken breast with a thallium spike deposited within the tissue. It is believed that the LA-LS-APGD-MS could be a valuable methodology for the simultaneous mapping of elemental and molecular species from a variety of samples.
... Paleontological objects (fossilized remains of animals and plants) have the potential to preserve remnant chemistry of the original organism (some constrained by specific biomarkers). Such fossils include mineralized soft Sciau et al. (2006), Liu et al. (2007), Lynch et al. (2007), Mirguet (2009), Leon et al. (2010, Jackson et al. (2013Jackson et al. ( , 2014Jackson et al. ( , 2017, Dejoie et al. (2014aDejoie et al. ( , b, 2015, Leon et al. (2015), and Bertrand et al. (2017) Advanced Photon Source ( 1-5 μm 2 Dredge et al. (2015Dredge et al. ( , 2017, MacLeod (2015), Popelka-Filcoff et al. (2015, Jones et al. (2016), Thurrowgood et al. (2016, Alfeld andde Viguerie (2017), de Jonge et al. (2017), Sharp-Paul (2017), Kirkwood et al. (2018), Ryan et al. ( , 2014Ryan et al. ( , 2018, Paterson et al. (2011), andHoward et al. (2012) XAS Riesemeier et al. (2005), Reiche et al. (2006Reiche et al. ( , 2011, and Radtke et al. (2013Radtke et al. ( , 2016 CHESS μm Swanston et al. (2012Swanston et al. ( , 2015, Michelin et al. (2013), Rouchon and Bernard (2015), and Alleon et al. (2016aand Alleon et al. ( , 2017 Canadian Light Source ( Michelin et al. (2013), Rouchon and Bernard (2015), Alleon et al. (2016aAlleon et al. ( , 2017, and Gueriau et al. (2017) 11ID-1 SGM ∼20-100 μm diameter Bergmann ( , 2007Bergmann ( , 2011, Bergmann and Knox (2009, Larson et al. (2010), Sadeghi and Bergmann (2010), Edwards et al. (2011aEdwards et al. ( , b, 2013Edwards et al. ( , 2014Edwards et al. ( , 2016Edwards et al. ( , 2018, Wogelius et al. (2011), Manning et al. (2013), Anne et al. (2014Anne et al. ( , 2017Anne et al. ( , 2018, Barden et al. (2015a, b), Egerton et al. (2015), Harazim et al. (2015), Gueriau et al. (2017), and Gibson et al. (2018) 10-2 Bertrand et al. (2011), andHoerlé et al. (2016) tissue that is not seen in the visible light spectrum and is often overlooked in such fossils. This additional information can lead to a better understanding of the pigmentation, anatomy, development and growth stage, diet, and even health of the organism prior to death. ...
... WD-XRF is developed for qualitative and quantitative analyses of elements with atomic number ≥ 4 (Be), which features the quantitative function provided that samples are properly prepared and calibration is strictly operated; while ED-XRF is applicable for qualitative and semi-quantitative analyses of elements from atomic number 9 (F) to 92 (U) in principle [25], which features quick and sensitive measurement without pretreating or touching samples, just fitting in with the needs of the museum field [24]. The metallic elements in alloy-based artefacts [26,27], antique polychromy [28], paintings [29,30] and porcelains [31,32] were all successfully detected by different types of XRF measurement. Compared with WD-XRF, ED-XRF is commoner in the museum field due to lower cost, simpler structure and easier operation as well. ...
Nine gemstone samples were analysed by using a portable X-ray fluorescence–X-ray diffraction (XRF–XRD) system without any destructive preparation processes. The samples were measured by groups based on the transparency and the complexity of molecular structure. The XRF and the XRD measurements for each sample were performed simultaneously. The key experimental parameters were optimized in order to obtain XRD patterns acceptable for phase identification in a limited time. The XRF spectrum of each sample was analysed first to acquire the elemental composition qualitatively, and the information was then applied to refining possible phases. The phase analysis process of each sample was described in detail and the most likely phases were determined. Normal XRD experiments were conducted in order to verify the results. Advantages, disadvantages and applicable range of the system were analysed. The results indicate that the portable XRF–XRD system can be applied to identifying particular gemstones effectively, while single-crystal gems may not be identified very well. Wider recognition and application of the portable XRF–XRD system in cultural heritage and gemological fields call for hardware development, software updating and more real application cases.
... For many centuries these material expressions were thought to have been monochromatic-given the lack of empirical evidence confirming their polychromy; a paradigmatic illustration of a past idealized as pure and white [1,2]. These works are now seen in their original polychrome as the result of varied chemical analyses [3,4]. In a similar fashion, the Pre- followers to, "undo the vault where the idol was and break him in front of everyone" [32:133] (S1 Text). ...
Pachacamac is the name of the 15th-16th century Inca sanctuary on the Peruvian coast as well as the name of one of the principal oracles of Inca divinities. This effigy would have been destroyed by Pizarro in 1533 during his visit to the great monumental complex, and as such the originality and antiquity of the wooden statue—the so-called Pachacamac Idol—have been the subject of much controversy and debate. We present here previously unpublished dates that confirm its manufacture during the Middle Horizon (AD 500–1000), as well as evidence of its original polychromy. Traces of colors were observed on its different sections with portable microscopy and analyses with two different X-Ray Fluorescence spectrometry techniques, leading to identification of yellow, white, and red mineral pigments, including the presence of cinnabar. Dated between the 8th and 9th centuries, the statue would have been worshipped for almost 700 years, from the time of its creation to the time of the Spanish conquest, when Pachacamac was a major place of pilgrimage. These data not only offer a new perspective on Pachacamac’s emblematic sacred icon, but also on the colorful practices of the Pre-Hispanic Andes.
... Paleontological objects (fossilized remains of animals and plants) have the potential to preserve remnant chemistry of the original organism (some constrained by specific biomarkers). Such fossils include mineralized soft Sciau et al. (2006), Liu et al. (2007), Lynch et al. (2007), Mirguet (2009), Leon et al. (2010, Jackson et al. (2013Jackson et al. ( , 2014Jackson et al. ( , 2017, Dejoie et al. (2014aDejoie et al. ( , b, 2015, Leon et al. (2015), and Bertrand et al. (2017) Advanced Photon Source ( 1-5 μm 2 Dredge et al. (2015Dredge et al. ( , 2017, MacLeod (2015), Popelka-Filcoff et al. (2015, Jones et al. (2016), Thurrowgood et al. (2016, Alfeld andde Viguerie (2017), de Jonge et al. (2017), Sharp-Paul (2017), Kirkwood et al. (2018), Ryan et al. ( , 2014Ryan et al. ( , 2018, Paterson et al. (2011), andHoward et al. (2012) XAS Riesemeier et al. (2005), Reiche et al. (2006Reiche et al. ( , 2011, and Radtke et al. (2013Radtke et al. ( , 2016 CHESS μm Swanston et al. (2012Swanston et al. ( , 2015, Michelin et al. (2013), Rouchon and Bernard (2015), and Alleon et al. (2016aand Alleon et al. ( , 2017 Canadian Light Source ( Michelin et al. (2013), Rouchon and Bernard (2015), Alleon et al. (2016aAlleon et al. ( , 2017, and Gueriau et al. (2017) 11ID-1 SGM ∼20-100 μm diameter Bergmann ( , 2007Bergmann ( , 2011, Bergmann and Knox (2009, Larson et al. (2010), Sadeghi and Bergmann (2010), Edwards et al. (2011aEdwards et al. ( , b, 2013Edwards et al. ( , 2014Edwards et al. ( , 2016Edwards et al. ( , 2018, Wogelius et al. (2011), Manning et al. (2013), Anne et al. (2014Anne et al. ( , 2017Anne et al. ( , 2018, Barden et al. (2015a, b), Egerton et al. (2015), Harazim et al. (2015), Gueriau et al. (2017), and Gibson et al. (2018) 10-2 Bertrand et al. (2011), andHoerlé et al. (2016) tissue that is not seen in the visible light spectrum and is often overlooked in such fossils. This additional information can lead to a better understanding of the pigmentation, anatomy, development and growth stage, diet, and even health of the organism prior to death. ...
... V. Brinkmann has since 1981 studied in detail the sculptures of the Temple of Aphaia in Aegina and the Greek tombstones in Munich sculpture Museum and focused on the application of new methods in photographic technique to the discovery and documentation of ancient colours with emphasis on their potential diagonal lighting (Vlasopoulou 2012;Brinkmann 2007). As for Delphi archaic monuments with coloured remains notable is the extensive report to the multi-coloured frieze of the Siphnian treasury (Brinkmann 1994;Alfeld et al., 2017). ...
Non-destructive analysis by means of portable X-ray flourescence (pXRF) and Raman spectroscopy of color traces on sculptures and architectural parts from the Delphi Museum, Phokis, Greece, are presented. These sculptures and architectural parts are dated to the Archaic period (7th-6th c. B.C.). The main question to be answered is the mineral/pigment used for each part and therefore to reconstruct the color palette of the artists. For this research, sixteen archaeological exhibits of the Delphi museum were analyzed with two different spectroscopies, and the white, red, black, yellow and blue pigments were identified.
... For a 300 s measurement they were found to be between 120 ppm (Ca, Z = 20) and 22 ppm (Cu, Z = 29) for elements heavier than Ca (Z = 20). The instrument has been previously described elsewhere [11]. ...
We present here the combination of in situ non invasive techniques to investigate a precious 15th century illuminated manuscript of Petrarch’s work, De remediis utriusque fortunae held in the Méjanes library in Aix-en-Provence (France). X-Ray fluorescence spectroscopy, mapping and point analysis, and visible reflectance hyperspectral imaging allow an unprecedented analysis of this manuscript. They provide new clues for its attribution by revealing a partly hidden coat of arms and describing the illuminator’s palette and techniques in detail. We reveal the identity of the first possessor of this manuscript, Tanguy IV du Châtel, known as a 15th century bibliophile close to Louis XI. This information is a further element contributing to the attribution of the richly illuminated folio 6 of this manuscript to François Le Barbier. Pigments and dyes used for this folio have been investigated with particular emphasis on the study of the superimposed colours thus providing a better understanding of the artist’s technique and know-how.
The mission of the Cultural Heritage Network of the Italian Institute of Nuclear Physics (INFN-CHNet) is presented here through a “virtuous” example: the activity related to the Macro-X-Ray Fluorescence (MA-XRF) scanner. The main focus of INFN-CHNet is the collaboration and sharing of knowledge among the network members, to better address the issues of Cultural Heritage operators, while the fields of activity are research (instrumental development and data management), analysis of cultural objects, education of young scholars and professionals, and dissemination to the general public. In this context, the MA-XRF scanner exemplifies the objectives of INFN-CHNet, being the first instrument developed, tested and optimised jointly by several INFN-CHNet partners. It was designed to be an open (free access to information on processes, components and materials), low-cost system, based on sustainability and interoperability, and modular. All these features allow for easy replication of instruments in any node of the network or reuse of system/subsystem also in different projects. Moreover, for the MA-XRF scanner, the whole path from data acquisition to their storage, management and visualisation/reuse has been addressed. The activities related to the scanner clearly demonstrate the effectiveness of the approach of CHNet in all the issues that arise in conservation and study of CH.
X-ray fluorescence (XRF) spectroscopy is a common technique in the field of heritage science. However, data processing and data interpretation remain a challenge as they are time consuming and often require a priori knowledge of the composition of the materials present in the analyzed objects. For this reason, we developed an open-source, unsupervised dictionary learning algorithm reducing the complexity of large datasets containing 10s of thousands of spectra and identifying patterns. The algorithm runs in Julia, a programming language that allows for faster data processing compared to Python and R. This approach quickly reduces the number of variables and creates correlated elemental maps, characteristic for pigments containing various elements or for pigment mixtures. This alternative approach creates an overcomplete dictionary which is learned from the input data itself, therefore reducing the a priori user knowledge. The feasibility of this method was first confirmed by applying it to a mock-up board containing various known pigment mixtures. The algorithm was then applied to a macro XRF (MA-XRF) data set obtained on an 18th century Mexican painting, and positively identified smalt (pigment characterized by the co-occurrence of cobalt, arsenic, bismuth, nickel, and potassium), mixtures of vermilion and lead white, and two complex conservation materials/interventions. Moreover, the algorithm identified correlated elements that were not identified using the traditional elemental maps approach without image processing. This approach proved very useful as it yielded the same conclusions Ras the traditional elemental maps approach followed by elemental maps comparison but with a much faster data processing time. Furthermore, no image processing or user manipulation was required to understand elemental correlation. This open-source, open-access, and thus freely available code running in a platform allowing faster processing and larger data sets represents a useful resource to understand better the pigments and mixtures used in historical paintings and their possible various conservation campaigns.
Archaeology, tasked with unraveling the mystery of human development through its fragmented material remains, has relied on chemical methods and instrumentation to characterize, date, and authenticate material remains for over two hundred years. Because archaeology lies at the intersection between science and the humanities, it provides a unique topic to engage both chemistry majors and nonmajors in the study of chemistry. Archaeological museums, natural history collections, library special collections, and ethnographic assemblages provide additional opportunities for interdisciplinary programing. Through these collaborations, students can provide museum and library special collection directors with critical information on an artifact or specimen’s chemical composition and previous preservation treatments. Such data can prove invaluable in the authentication and safe handling of these items, in addition to assisting with historical and archaeological research. Furthermore, students receive the benefits of application-based chemical education including increased persistence, improved assessment outcomes, and reduced failure rates. This chapter highlights archaeological themed activities, labs, and a course developed over the last ten years for use from the introductory to advanced levels for both majors and nonmajors. Within this work, archaeology serves as a vehicle to introduce key chemical concepts, provide students project-based instrumentation experiences through which they can answer pertinent scientific and archaeological questions, and facilitates research opportunities outside the traditional laboratory.
This chapter focuses on the basic principles of X-ray fluorescence (XRF) and micro-XRF imaging applicable to cultural heritage research, presenting basic figures of merit and application examples based on the use of advanced laboratory and synchrotron radiation sources. Related methods of analysis making use of absorption edge phenomena by X-ray absorption spectroscopy, including X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy will also be discussed.
Series Elastic Actuators (SEAs) are multi-degree-of-freedom spring-mass-damper systems that employ elastic transmission elements to reduce mechanical impedance and buffer energy from motor (input) to load (output). This work deals with the mathematical modeling of SEAs and their sizing for given application requirements. In designing traditional actuation systems a common approach is to optimize the speed ratio of the transmission with respect to a given figure of merit, such as the motor rated torque or power, once the output load torque and motion trajectories are given. Taking inspiration from existing techniques developed for the sizing of traditional actuators having just one degree of freedom, a new approach is presented here for two degrees of freedom SEAs, which enables the designer to optimally select at the same time both the ratio and the compliance of the elastic transmission.
The nonplanar shape of a painting as well as practical constraints often result in the painting's surface not being parallel to the plane in that the measurement head of a MA-XRF scanner is being moved. Changing the working distance affects the measurement geometry, so that the sensitivity for the same element may vary throughout the investigated area and induce visible artifacts. These artifacts are especially visible when different scans of the same painting are stitched together. In this article, we present an approach to correct for the variation of the measurement distance. We explored using an intrinsic part of the XRF data set, the Ar signal from the air, to estimate the distance between surface and instrument. The model is developed based on fundamental parameter calculations and a measurement of a NIST 610 standard and is verified on a set of scans of Rembrandt's 'Portrait of Oopjen Coppit (1611-1689)'.
The X‐Ray Fluorescence (XRF) scanning spectrometer developed in the framework of Cultural Heritage Network ‐ National Institute of Nuclear Physics, is specifically customised for cultural heritage applications, designed with a focus on having a lightweight scanner (weighing approximately 10 kg), easy to handle and thus easily transportable in two medium‐sized boxes. The research presented here deals with the study of a set of choir books preserved in the Abbey of San Giorgio Maggiore on the homonymous island in Venice. Produced for the Abbey itself from the mid‐15th century onwards, the manuscripts have never left the island, making the study of the materials of particular interest as they have undergone little or no modification over time. During their history in the Abbey, however, the volumes have been disassembled and reassembled in various ways, bringing complexity to the current cataloguing work. Thus, analytical investigations of the pigments and painting techniques might help identify the original arrangement of displaced leaves and provide evidence for the attribution of individual illuminations to certain artists. Thanks to its easy transportability, it was possible to take the scanner to the small island by means of the water‐based Venetian public transport. Selected results are presented, derived from the high‐quality MA‐XRF maps obtained.
The study presents the application of combined micro-Spatially Offset Raman Spectroscopy (micro-SORS) and confocal X-ray fluorescence (confocal XRF) to the non-destructive investigation of micrometer scale stratified painted systems. Micro-SORS can be applied in situations where a high turbidity of layers prevents the acquisition of conventional Raman signals from depth and in the presence of Raman scattering compounds, facilitating highly chemically specific (molecular) characterization of the layers. In contrast, confocal XRF provides elemental information on a well-defined volume at a given depth. In this study, selected specimens have been analysed with both methods; molecular and elemental data have been compared and integrated for a comprehensive characterization of the stratigraphy. This dual approach represents a new analytical modality in the area of Cultural Heritage and is also beneficial in areas where non-destructive interrogation of thin layers and films is required.
This review describes advances in the XRF group of techniques published approximately between April 2017 and March 2018. The review is selective with the aim of providing a critical insight into developments in instrumentation, methodologies and data handling that represent a significant advance in XRF spectrometry. It is not the intention of the review to cover comprehensively the applications of XRF techniques except in those cases where the non-destructive and remote sensing nature of XRF analysis makes it particularly valuable and the method of choice. These applications concern samples which are irreplaceable and of great cultural value such as works of art and archaeological artefacts.
The pigment use in the Tomb of the Reliefs (fourth century BC) and four other tombs (seventh to fourth century BC) in the Etruscan Banditaccia Necropolis near Cerveteri, Italy, has been investigated. We made use of X‐ray fluorescence (XRF) and Raman spot analysis, XRF imaging, infrared luminescence and photography supported by Dstretch contrast enhancement. We identified the use of haematite, goethite, calcite, carbon black, manganese oxide, Tyrian purple, and Egyptian blue, with the last three only found under the central burial place of the Tomb of the Reliefs. The tuff in which these tombs were cut proved to be a significant challenge for XRF analysis as the signals of Ca, Mn, and Fe vary strongly due to the heterogeneity of the stone, so that it is difficult to distinguish between signals from the tuff and the pigments. Finally, we show that lightweight instruments transported in check‐in luggage may not answer all questions on pigment use but do provide additional insights.
In the past decade macroscopic X-ray fluorescence imaging (MA-XRF) has become established as a method for the nonin-vasive investigation of flat painted surfaces, yielding large scale elemental maps. MA-XRF is limited by a lack of specificity, only allowing for indirect pigment identification based on the simultaneous presence of chemical elements. The high speci-ficity of X-ray powder diffraction (XRPD) mapping is already being exploited at synchrotron facilities for investigations at the (sub)microscopic scale, but the technique has not yet been employed using lab sources. In this paper we present the de-velopment of a novel MA-XRPD/XRF instrument based on a laboratory X-ray source. Several combinations of X-ray sources and area detectors are evaluated in terms of their spatial and angular resolution and their sensitivity. The highly-specific imaging capability of the combined MA-XRPD/XRF instrument is demonstrated on a 15th/16th century illuminated manuscript directly revealing the distribution of a large number of inorganic pigments, including the uncommon yellow pig-ment massicot (o-PbO). The case study illustrates the wealth of new mapping information that can be obtained in a nonin-vasive manner using the laboratory MA-XRPD/XRF instrument.
Reading the content of hidden texts from ancient manuscripts has become an increasingly important endeavor thanks to the variety of non-destructive analytical tools and image processing routines available for this task. In this study, portable macro X-Ray Fluorescence (MA-XRF-tube), Visible Hyperspectral Imaging (HSI) together with Synchrotron based macro X-Ray Fluorescence (MA-XRF-SR) are combined with signal processing methods to reveal the biography of a degraded manuscript recycled as binding material for a 16th century printed edition of Hesiod’s Works and Days. The analytical techniques allow visualizing the hidden text, revealing passages from the Institutes Justinian, a 6th century A.D codification of the Roman Law, with further marginal comments on medieval Canon Law. In addition, the identification of the materials (e.g. pigments, inks) part of the original manuscript together with their sequence of use are revealed: i) the preparation of the parchment using a Ca-based preparation layer, ii) drawing of ruled guide lines, using a Pb-based pen or ink, iii) writing of the main text using a rich Fe-gall ink with modulating color pigments (Hg-, Cu- and Pb- based) and iv) addition of two types of comments to the main text, one of the ink used for the comments being a Fe-gall ink rich in Cu.
Technical progress in the fields of X-ray sources, optics and detectors is constantly enhancing the pace of data acquisition in XRF imaging. This enlarges the size of the hyperspectral datasets and the number of their sub-parts. This paper describes the challenges in processing large XRF datasets featuring several million pixels/spectra and the strategies developed to overcome them. During the investigation of historical paintings by scanning macro-XRF the main challenges are the correct identification of all spectral features in a dataset and its timely processing. For the identification of spectral features different approaches are discussed, i.e. the use of sum spectra, maximum pixel spectra and of χr2 maps. For the time-efficient, artefact-free evaluation of XRF imaging data, different software packages are evaluated and intercompared (AXIL, PyMCA, GeoPIXE and the in-house written datamuncher). The process of data evaluation is illustrated on a large dataset (3.4 MPixels) acquired during the investigation of a version of Caravaggio's Supper at Emmaus (143 × 199.5 cm2). This 17th century painting is currently the largest object entirely scanned with macroscopic XRF.
Samples with non-planar surfaces present challenges for X-ray fluorescence imaging analysis. Here, approximations are derived to describe the modulation of fluorescence signals by surface angles and topography, and suggestions are made for reducing this effect. A correction procedure is developed that is effective for trace element analysis of samples having a uniform matrix, and requires only a fluorescence map from a single detector. This procedure is applied to fluorescence maps from an incised gypsum tablet.
Paintings are near-planar objects with material characteristics that vary widely. The fact that paint has a material presence is often overlooked, mostly because we often encounter these artworks in the form of two-dimensional reproductions. Capturing paintings in the third dimension is not only important for study, restoration and conservation, but it also inspires 3D printing methods1, particularly through the high demands it makes on reproducing color, gloss and texture.
A hybrid solution between fringe projection and stereo imaging is proposed as 3D imaging method, with a setup involving two cameras and a projector. Fringe projection is aided by sparse stereo matching to serve as image encoder. These encoded images processed by the stereo cameras solve the correspondence problem in stereo matching, leading to a dense and accurate topographical map, while simultaneously capturing the composition of the painting in full color.
The topographical map and color data are used to make hardcopy 3D reproductions, using a specially developed printing system. Several paintings by Dutch masters Rembrandt and Van Gogh have been scanned and reproduced using this technique. These 3D printed reproductions have been evaluated by experts, both individually and in a side-by-side comparison with the original.
The analytical aspects of the investigation of 'Flower Still Life' by Vincent van Gogh and its underlying composition, showing two wrestlers by scanning macro-X-ray Fluorescence Analysis (MA-XRF) was reported. In MA-XRF the painting is excited by an X-ray millibeam to emit X-ray fluorescence radiation. Through the energy of the recorded fluorescence radiation the elements present in the analyzed spot can be identified. The painting was mounted on a motor stage behind the normal experimental table and moved continuously through the beam for scanning. The beam size was defined by a set of slits placed at the end of the experimental table. MA-XRF scans were performed with a step size of 1 mm and a dwell time of 3.6 s. The sample was cross-sectioned and examined using high-resolution microscopic methods. The correction of absorption effects in the Zn-maps allowed to remove otherwise misleading artifacts from hidden layers, so that a more realistic impression of the hidden portrait is gained.
Scanning macro-X-ray fluorescence analysis (MA-XRF) is rapidly being established as a technique for the investigation of historical paintings. The elemental distribution images acquired by this method allow for the visualization of hidden paint layers and thus provide insight into the artist's creative process and the painting's conservation history. Due to the lack of a dedicated, commercially available instrument the application of the technique was limited to a few groups that constructed their own instruments. We present the first commercially available XRF scanner for paintings, consisting of an X-ray tube mounted with a Silicon-Drift (SD) detector on a motorized stage to be moved in front of a painting. The scanner is capable of imaging the distribution of the main constituents of surface and sub-surface paint layers in an area of 80 by 60 square centimeters with dwell times below 10 ms and a lateral resolution below 100 μm. The scanner features for a broad range of elements between Ti (Z = 22) and Mo (Z = 42) a count rate of more than 1000 counts per second (cps)/mass percent and detection limits of 100 ppm for measurements of 1 s duration. Next to a presentation of spectrometric figures of merit, the value of the technique is illustrated through a case study of a painting by Rembrandt's student Govert Flinck (1615–1660).
Interpretation of X-ray fluorescence images of archeological artifacts is complicated by the presence of surface relief and roughness. Using two symmetrically arranged fluorescence detectors in a back-reflection geometry, the proper X-ray fluorescence yield can be distinguished from intensity variations caused by surface topography. This technique has been applied to the study of Roman inscriptions on marble.
3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a “sensor fusion” approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications.
The X-ray fluorescence imaging technique allows not only imaging but also identification of the hidden paint layers what makes it much more versatile tool than X-ray radiography. One of main disadvantages of this method is fact that the characteristic X-rays from deeper paint layers are absorbed in the covering layers. This effect manifests itself in a form of artefacts that impede proper interpretation of the acquired images. In this work it is shown that the methodology of correction of the inter-layer absorption effects can be extended to the case of polychromatic excitation. Additionally, the new approach of determination of the optimal correction parameters was presented. The methodology was tested with use of test painting and mock-up painting measured with table-top micro-XRF setup.
Macro-X-ray fluorescence (XRF) is a newly commercially available research tool very useful in the examination of artwork. Its novelty lies in its ability to create maps of the distribution of chemical elements on scales of a few milimetres. In this contribution, its use together with optical coherence tomography (OCT) in the inspection of an illuminated manuscript is reported for the first time. The former technique is used both for mapping the elemental distribution over large parts of the folios - including illuminated initials - and for quantitative analysis of the composition of the smalt pigment, as well as of changes in the composition of iron-gall ink at different pages. The latter, by providing cross-sectional images of painted details, helps in interpreting the XRF results. All of the results shown relate to the examination of a late sixteenth-century-illuminated parchment manuscript (a gradual) originating from the Convent of the Benedictine Sisters in Lviv in the Ukraine. © The International Institute for Conservation of Historic and Artistic Works 2015.
Hidden, sub-surface paint layers and features contain valuable information for the art-historical investigation of a painting's past and for its conservation for coming generations. The number of techniques available for the study of these features has been considerably extended in the last decades and established techniques have been refined.
This review focuses on mobile non-destructive subsurface imaging and depth profiling techniques, which allow for the in-situ investigation of easel paintings, i.e. paintings on a portable support.
Among the techniques discussed are: X-ray radiography and infrared reflectography, which are long established methods and are in use for several decades. Their capabilities of element/species specific imaging have been extended by the introduction of energy/wavelength resolved measurements.
Scanning macro-X-ray fluorescence analysis made it for the first time possible to acquire elemental distribution images in-situ and optical coherence tomography allows for the non-destructive study the surface paint layers in virtual cross-sections.
These techniques and their variants are presented next to other techniques, such as Terahertz imaging, Nuclear Magnetic Resonance depth profiling and established techniques for non destructive testing (thermography, ultrasonic imaging and laser based interference methods) applied in the conservation of historical paintings.
Next to selected case studies the capabilities and limitations of the techniques are discussed.
This work presents the recent developments of xraylib, an ANSI C library that provides convenient access to a large number of X-ray related databases, with a focus on quantitative X-ray fluorescence applications. The enhancements include improved X-ray fluorescence production cross sections that take into account cascade effects and M-lines, as well as revised line energies, atomic level widths, Compton broadening profiles etc. A full overview of the complete application programming interface is presented.
IntroductionBasic Principles X-ray Wavelength and Energy ScalesInteraction of X-rays with MatterPhotoelectric EffectScatteringBremsstrahlungSelection Rules, Characteristic Lines and X-ray SpectraFigures-of-merit for XRF SpectrometersInstrumentation X-ray SourcesX-ray DetectorsWavelength-dispersive XRFEnergy-dispersive XRFRadioisotope XRFTotal Reflection XRFMicroscopic XRFMatrix Effects Thin and Thick SamplesPrimary and Secondary Absorption, Direct and Third Element EnhancementData Treatment Counting StatisticsSpectrum Evaluation TechniquesQuantitative Calibration ProceduresError Sources in X-ray Fluorescence AnalysisSpecimen Preparation for X-ray FluorescenceAdvantages and Limitations Qualitative AnalysisDetection LimitsQuantitative ReliabilitySummary X-ray Wavelength and Energy ScalesInteraction of X-rays with MatterPhotoelectric EffectScatteringBremsstrahlungSelection Rules, Characteristic Lines and X-ray SpectraFigures-of-merit for XRF Spectrometers X-ray SourcesX-ray DetectorsWavelength-dispersive XRFEnergy-dispersive XRFRadioisotope XRFTotal Reflection XRFMicroscopic XRF Thin and Thick SamplesPrimary and Secondary Absorption, Direct and Third Element Enhancement Counting StatisticsSpectrum Evaluation TechniquesQuantitative Calibration ProceduresError Sources in X-ray Fluorescence AnalysisSpecimen Preparation for X-ray Fluorescence Qualitative AnalysisDetection LimitsQuantitative Reliability
This article illustrates the analysis by synchrotron micro-analytical techniques of an azurite painting presenting greenish
chromatic degradation. The challenge of the experiments was to obtain the spatial distribution of the degradation products
of azurite. Copper hydroxychlorides, carbonates and copper oxalates have been mapped by SR FTIR imaging of cross sections
in transmission mode. To complement the information, Py/GC/MS and GC/MS techniques were applied in order to characterize the
binding media and organic materials present as well as their degradation products. Results contribute to a better understanding
of the decay of blue areas in ancient paintings not only from the particular point of view of azurite weathering, but also
by adding information regarding the oxalates’ formation and their distribution in painting samples. Synchrotron radiation
demonstrates its capability for the mapping in painting cross sections.
A user friendly program for X-ray fluorescence analysis has been developed at the European Synchrotron Radiation Facility. The program allows interactive as well as batch processing of large data sets and it is particularly well suited for X-ray imaging. Its implementation of a complete description of the M shell is particularly helpful for analysis of data collected at low energies. The code is platform independent (Linux, Windows, MacOS X, Solaris …) and it is freely available for non-commercial use. Description of the algorithms used and practical examples are presented.
Quantitative estimate of elemental composition by spectroscopic and imaging techniques using X-ray fluorescence requires the availability of accurate data of X-ray interaction with matter. Although a wide number of computer codes and data sets are reported in literature, none of them is presented in the form of freely available library functions which can be easily included in software applications for X-ray fluorescence. This work presents a compilation of data sets from different published works and an xraylib interface in the form of callable functions. Although the target applications are on X-ray fluorescence, cross sections of interactions like photoionization, coherent scattering and Compton scattering, as well as form factors and anomalous scattering functions, are also available.
A newly developed spectrometer for energy-dispersive micro X-ray fluorescence spectrometry has been designed for the demands of archaeometry. ArtTAX combines the advantages of non-destructive and sensitive multi-elemental analysis at sub-mm resolution with the possibility of working outside the laboratory. The spectrometer consists of an air-cooled, low-power molybdenum tube, new generation polycapillary X-ray optics, a silicon drift detector without the need for liquid-nitrogen cooling, a CCD camera, and three light diodes for sample positioning. The motor-driven measurement head is fixed on a x,y,z-flexible tripod support which can be assembled and dismantled within minutes. The spot size of the primary X-ray beam was determined to be 94 microm for the Cu(Kalpha) energy, the detection limits are in a range of a few tens of microg g(-1) for the medium energy-range in glass. Additional open helium purging in the excitation and detection paths enables the determination of elements down to sodium, thus avoiding vacuum conditions or a size-limiting sample chamber. A selection of qualitative and quantitative results on pigment, metal, glass, and enamel analyses are presented to show the potential of ArtTAX in the field of art and archaeology.
The conservation of the polychromy of the terracotta army of the first Chinese emperor Qin Shihuangdi represents a special problem because of the deterioration of the ground layer consisting of organic material. This was triggered due to it having spent more than 2200 years in water-saturated soil. The consolidation of the polychromy was achieved through polymerisation of a specially adapted combination of monomers.
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