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“Optimization of mobile scanning macro-XRF systems for the in situ investigation of historical paintings”. Alfeld M, Janssens K, Dik J, de Nolf W, van der Snickt G, Journal of analytical atomic spectrometry 26, 899 (2011). http://doi.org/10.1039/C0JA00257G
Abstract: Elemental distribution maps are of great interest in the study of historical paintings, as they allow to investigate the pigment use of the artist, to image changes made in the painting during or after its creation and in some cases to reveal discarded paintings that were later over painted. Yet a method that allows to record such maps of a broad range of elements in a fast, non-destructive and in situ manner is not yet commonly available; a dedicated mobile scanning XRF instrument might fill this gap. In this paper we present three self-built scanning macro-XRF instruments, each based on the experience gained with its precursor. These instruments are compared in terms of sensitivity and limits of detection, which includes a discussion of the use of polycapillary optics and pinhole collimators as beam defining devices. Furthermore, the imaging capabilities of the instruments are demonstrated in three exemplary cases: (parts of) historical paintings from the 15th to the 19th century are examined. These cases illustrate the value of element specific distribution maps in the study of historical paintings and allow in the case of Vincent van Gogh's Patch of Grass a direct comparison between in situ and synchrotron based scanning macro-XRF.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 107
DOI: 10.1039/C0JA00257G
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“The use of microscopic X-ray diffraction for the study of HgS and its degradation products corderoite (\alpha-Hg3S2Cl2), kenhsuite (\gamma-Hg3S2Cl2) and calomel (Hg2Cl2) in historical paintings”. Radepont M, de Nolf W, Janssens K, van der Snickt G, Coquinot Y, Klaassen L, Cotte M, Journal of analytical atomic spectrometry 26, 959 (2011). http://doi.org/10.1039/C0JA00260G
Abstract: Since antiquity, the red pigment mercury sulfide (α-HgS), called cinnabar in its natural form or vermilion red when synthetic, was very often used in frescoes and paintings, even if it was known to suffer occasionally from degradation. The paint hereby acquires a black or silver-grey aspect. The chemical characterization of these alteration products is rather challenging mainly because of the micrometric size and heterogeneity of the surface layers that develop and that are responsible for the color change. Methods such as electron microscopy, synchrotron-based microscopic X-ray fluorescence, microscopic X-ray absorption near edge spectroscopy, Raman microscopy and secondary ion microscopy have been previously employed to identify the (Hg- and S-) compounds present and to study their co-localization. Next to these, also microscopic X-ray diffraction (XRD) (either by making use of laboratory X-ray sources or when used at a synchrotron facility) allows the identification of the crystal phases that are present in degraded HgS paint layers. In this paper we employ these various forms of micro-XRD to analyze degraded red paint in different paintings and compare the results with other X-ray based methods. Whereas the elemental analyses of the degradation products revealed, next to mercury and sulfur, the presence of chlorine, X-ray diffraction allowed the identification, next to α-HgS, of the Hg and S-containing compound calomel (Hg2Cl2) but also of the Hg, S and Cl-containing minerals corderoite (α-Hg3S2Cl2) and kenhsuite (γ-Hg3S2Cl2). These observations are consistent with X-ray absorption spectroscopy measurements performed at the S- and Cl-edges.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 40
DOI: 10.1039/C0JA00260G
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“James Ensor's pigment use: artistic and material evolution studied by means of portable X-ray fluorescence spectrometry”. van der Snickt G, Janssens K, Schalm O, Aibéo C, Kloust H, Alfeld M, X-ray spectrometry 39, 103 (2010). http://doi.org/10.1002/XRS.1235
Abstract: In this paper, portable X-ray fluorescence spectrometry (PXRF) was employed as a screening tool for determining and comparing the pigment use in a large series of paintings by the Belgian artist James Ensor (1860-1949). Benefits and drawbacks of PXRF as a method, and the instrument employed, are discussed from a practical, conservation and instrumental perspective. Regardless of several restrictions due to the set-up and/or the analytical method, it appeared feasible to document the evolution with time in Ensor's use of inorganic pigments and to correlate this technical evolution with stylistic developments, Nevertheless, it became clear that a full identification of all materials present can only be done by means of the analysis of (cross-sectioned) samples.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.298
Times cited: 25
DOI: 10.1002/XRS.1235
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“Recent trends in quantitative aspects of microscopic X-ray fluorescence analysis”. Janssens K, de Nolf W, van der Snickt G, Vincze L, Vekemans B, Terzano R, Brenker FE, Trends in analytical chemistry 29, 464 (2010). http://doi.org/10.1016/J.TRAC.2010.03.003
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 8.442
Times cited: 48
DOI: 10.1016/J.TRAC.2010.03.003
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“Enamels in stained glass windows: preparation, chemical composition, microstructure and causes of deterioration”. Schalm O, van der Linden V, Frederickx P, Luyten S, van der Snickt G, Caen J, Schryvers D, Janssens K, Cornelis E, van Dyck D, Schreiner M, Spectrochimica acta: part B : atomic spectroscopy 64, 812 (2009). http://doi.org/10.1016/j.sab.2009.06.005
Abstract: Stained glass windows incorporating dark blue and purple enamel paint layers are in some cases subject to severe degradation while others from the same period survived the ravages of time. A series of dark blue, greenblue and purple enamel glass paints from the same region (Northwestern Europe) and from the same period (16early 20th centuries) has been studied by means of a combination of microscopic X-ray fluorescence analysis, electron probe micro analysis and transmission electron microscopy with the aim of better understanding the causes of the degradation. The chemical composition of the enamels diverges from the average chemical composition of window glass. Some of the compositions appear to be unstable, for example those with a high concentration of K2O and a low content of CaO and PbO. In other cases, the deterioration of the paint layers was caused by the less than optimal vitrification of the enamel during the firing process. Recipes and chemical compositions indicate that glassmakers of the 1617th century had full control over the color of the enamel glass paints they made. They mainly used three types of coloring agents, based on Co (dark blue), Mn (purple) and Cu (light-blue or greenblue) as coloring elements. Bluepurple enamel paints were obtained by mixing two different coloring agents. The coloring agent for redpurple enamel, introduced during the 19th century, was colloidal gold embedded in grains of lead glass.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Vision lab
Impact Factor: 3.241
Times cited: 28
DOI: 10.1016/j.sab.2009.06.005
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“Characterization of a degraded cadmium yellow (CdS) pigment in an oil painting by means of synchrotron radiation based X-ray techniques”. van der Snickt G, Dik J, Cotte M, Janssens K, Jaroszewicz J, de Nolf W, Groenewegen J, van der Loeff L, Analytical chemistry 81, 2600 (2009). http://doi.org/10.1021/AC802518Z
Abstract: On several paintings of James Ensor (1860−1949), a gradual fading of originally bright yellow areas, painted with the pigment cadmium yellow (CdS), is observed. Additionally, in some areas exposed to light, the formation of small white-colored globules on top of the original paint surface is observed. In this paper the chemical transformation leading to the color change and to the formation of the globules is elucidated. Microscopic X-ray absorption near-edge spectroscopy (ì-XANES) experiments show that sulfur, originally present in sulfidic form (S2−), is oxidized during the transformation to the sulfate form (S6+). Upon formation (at or immediately below the surface), the highly soluble cadmium sulfate is assumed to be transported to the surface in solution and reprecipitates there, forming the whitish globules. The presence of cadmium sulfate (CdSO4·2H2O) and ammonium cadmium sulfate [(NH4)2Cd(SO4)2] at the surface is confirmed by microscopic X-ray diffraction measurements, where the latter salt is suspected to result from a secondary reaction of cadmium sulfate with ammonia. Measurements performed on cross sections reveal that the oxidation front has penetrated into the yellow paint down to ca. 1−2 ìm. The morphology and elemental distribution of the paint and degradation product were examined by means of scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS) and synchrotron radiation based micro-X-ray fluorescence spectrometry (SR ì-XRF). In addition, ultraviolet-induced visible fluorescence photography (UIVFP) revealed itself to be a straightforward technique for documenting the occurrence of this specific kind of degradation on a macroscale by painting conservators.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 91
DOI: 10.1021/AC802518Z
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“Combined micro-XRF/XRPD tomography on historical and modern paint multilayer samples at Beamline L”. de Nolf W, Jaroszewicz J, van der Snickt G, Janssens K, Farnell S, Klaassen L page 1633 (2008).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“High-E scanning m-XRF experiment on test paintings”. Dik J, Janssens K, van der Snickt G, Wallert A, Rickers K, Falkenberg G page 1589 (2008).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“μ-XRF/μ-RS vs. SR μ-XRD for pigment identification in illuminated manuscripts”. van der Snickt G, de Nolf W, Vekemans B, Janssens K, Applied physics A : materials science &, processing 92, 59 (2008). http://doi.org/10.1007/S00339-008-4447-9
Abstract: For the non-destructive identification of pigments and colorants in works of art, in archaeological and in forensic materials, a wide range of analytical techniques can be used. Bearing in mind that every method holds particular limitations, two complementary spectroscopic techniques, namely confocal ì-Raman spectroscopy (ì-RS) and ì-X-ray fluorescence spectroscopy (ì-XRF), were joined in one instrument. The combined ì-XRF and ì-RS device, called PRAXIS unites both complementary techniques in one mobile setup, which allows ì- and in situ analysis. ì-XRF allows one to collect elemental and spatially-resolved information in a non-destructive way on major and minor constituents of a variety of materials. However, the main disadvantages of ì-XRF are the penetration depth of the X-rays and the fact that only elements and not specific molecular combinations of elements can be detected. As a result ì-XRF is often not specific enough to identify the pigments within complex mixtures. Confocal Raman microscopy (ì-RS) can offer a surplus as molecular information can be obtained from single pigment grains. However, in some cases the presence of a strong fluorescence background limits the applicability. In this paper, the concrete analytical possibilities of the combined PRAXIS device are evaluated by comparing the results on an illuminated sheet of parchment with the analytical information supplied by synchrotron radiation ì-X-ray diffraction (SR ì-XRD), a highly specific technique.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.455
Times cited: 56
DOI: 10.1007/S00339-008-4447-9
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“Micro-Raman analysis for the identification of pigments from 19th and 20th century paintings”. Aibéo CL, Goffin S, Schalm O, van der Snickt G, Laquière N, Eyskens P, Janssens K, Journal of Raman spectroscopy 39, 1091 (2008). http://doi.org/10.1002/JRS.1990
Abstract: In this article, results using confocal µ-Raman to analyse the cross-section of paint samples are presented. Results obtained with light microscopy, scanning electron microscopy (SEM) combined with an energy dispersive X-ray analysis (EDX) and micro-X-ray fluorescence (µ-XRF) are mentioned and compared to the ones obtained with confocal (MRS). In some cases, pigment identification was possible only by combining analytical results from different techniques. The samples were drawn from five paintings belonging to the Academy of Fine Arts of Antwerp, which are part of a collection of 34 paintings made by students from the Academy between 1819 and 1920. Since, on the one hand, the painting techniques and materials, especially pigments, used in this period are still not completely known, and on the other hand, this collection constitutes a very important and reliable resource of information, these paintings were chosen for a systematic investigation. They represent the evolution of painting in Belgium over approximately a century.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.969
Times cited: 28
DOI: 10.1002/JRS.1990
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“Visualization of a lost painting by Vincent van Gogh using synchrotron radiation based X-ray fluorescence elemental mapping”. Dik J, Janssens K, van der Snickt G, van der Loeff L, Rickers K, Cotte M, Analytical chemistry 80, 6436 (2008). http://doi.org/10.1021/AC800965G
Abstract: Vincent van Gogh (1853−1890), one of the founding fathers of modern painting, is best known for his vivid colors, his vibrant painting style, and his short but highly productive career. His productivity is even higher than generally realized, as many of his known paintings cover a previous composition. This is thought to be the case in one-third of his early period paintings. Van Gogh would often reuse the canvas of an abandoned painting and paint a new or modified composition on top. These hidden paintings offer a unique and intimate insight into the genesis of his works. Yet, current museum-based imaging tools are unable to properly visualize many of these hidden images. We present the first-time use of synchrotron radiation based X-ray fluorescence mapping, applied to visualize a womans head hidden under the work Patch of Grass by Van Gogh. We recorded decimeter-scale, X-ray fluorescence intensity maps, reflecting the distribution of specific elements in the paint layers. In doing so we succeeded in visualizing the hidden face with unprecedented detail. In particular, the distribution of Hg and Sb in the red and light tones, respectively, enabled an approximate color reconstruction of the flesh tones. This reconstruction proved to be the missing link for the comparison of the hidden face with Van Goghs known paintings. Our approach literally opens up new vistas in the nondestructive study of hidden paint layers, which applies to the oeuvre of Van Gogh in particular and to old master paintings in general.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 178
DOI: 10.1021/AC800965G
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“Pigment identification by scanning μ-XRF/μ-XRD”. de Nolf W, Vekemans B, Janssens K, van der Snickt G, Falkenberg G (2007).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“The SALUT project : study of advanced laser techniques for the uncovering of polychromed works of art”. van der Snickt G, de Boeck A, Keutgens K, Anthierens D, 116, 151 (2007)
Abstract: In order to find out whether the existing laser systems can be employed to remove superimposed layers of paint on secco wall paintings in a selective way, laser tests were carried out on three types of prepared samples simulating three stratigraphies that are frequently encountered in practice. OM, EPMA, colorimetry, mu Raman, and FT-IR were used to evaluate the results. It was found that Q-switched Nd:YAG lasers emitting at 1,064 nm could be employed to remove unwanted layers of oil paint and limewash, but the treatment of large areas requires implementation of a computer-controlled X-Y-Z station in order to control the parameters. However, the applicability of this technique will remain limited as ablation at the established optimum parameters implied a discoloration of the pigments cinnabar, yellow ochre, and burnt sienna. Moreover, it was observed that no ablation took place when the limewash thickness exceeds 25 mu m. Unwanted layers of acrylic could be removed in an efficient way with an excimer laser emitting at 193 nm.
Keywords: P1 Proceeding; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Blue enamel on sixteenth- and seventeenth-century window glass : deterioration, microstructure, composition and preparation”. van der Snickt G, Schalm O, Caen J, Janssens K, Schreiner M, Studies in conservation 51, 212 (2006). http://doi.org/10.1179/SIC.2006.51.3.212
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 0.578
Times cited: 8
DOI: 10.1179/SIC.2006.51.3.212
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“Enamels in stained-glass windows : preparation, chemical composition, microstructure and causes of deterioration”. Caen J, Schalm O, van der Snickt G, van der Linden V, Frederickx P, Schryvers D, Janssens K, Cornelis E, van Dyck D, Schreiner M, , 121 (2005)
Keywords: P3 Proceeding; Art; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Vision lab
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