“Deeply colored and black-appearing Roman glass : a continued research”. Cagno S, Cosyns P, Izmer A, Vanhaecke F, Nys K, Janssens K, Journal of archaeological science 42, 128 (2014). http://doi.org/10.1016/J.JAS.2013.11.003
Abstract: In the context of archaeological and historical assessment of Roman black-appearing glass, the chemical and physical characterization of a large collection of samples originating from various areas of the Roman Empire has been gathered over the past years to (i) verify whether a minor segment of the overall Roman glass production can help in determining possible diachronic changes in Roman imperial glass production (1st century AD – 5th century AD) and (ii) reveal regional compositional differences. In this paper, the latest results on the chemical composition of an additional 44 black-appearing Roman glass samples are presented, together with general conclusions based upon the entire compositional dataset of over 400 analyzed black glass samples. The results show that the Roman black glass is obtained through several glass compositions with a specific chronological, geographical and typological distribution. (C) 2013 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Philosophy; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.602
Times cited: 18
DOI: 10.1016/J.JAS.2013.11.003
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“Deeply coloured and black glass in the Northern provinces of the Roman Empire : differences and similarities in chemical composition before and after AD 150”. van der Linden V, Cosyns P, Schalm O, Cagno S, Nys K, Janssens K, Nowak A, Wagner B, Bulska E, Archaeometry 51, 822 (2009). http://doi.org/10.1111/J.1475-4754.2008.00434.X
Abstract: In this work we attempt to elucidate the chronological and geographical origin of deeply coloured and black glass dating between 100 bc and ad 300 on the basis of their major and trace element compositions. Samples from the western and eastern parts of the Roman Empire were analysed. Analytical data were obtained by means of a scanning electron microscope – energy-dispersive system (SEM-EDS, 63 samples analysed) and laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS, 41 samples analysed). Among the glass fragments analysed, dark brown, dark purple and dark green hues could be distinguished. Only among the dark green fragments could a clear compositional distinction be observed between fragments dated to the periods before and after ad 150. In the early samples (first century bc to first century ad), iron, responsible for the green hue, was introduced by using impure sand containing relatively high amounts of Ti. In contrast, a Ti-poor source of iron was employed, containing Sb, Co and Pb in trace quantities, in order to obtain the dark green colour in the later glass samples. The analytical results obtained by combining SEM-EDS and LA-ICP-MS are therefore consistent with a differentiation of glassmaking recipes, detectable in glass composition, occurring in the period around ad 150.
Keywords: A1 Journal article; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.47
Times cited: 39
DOI: 10.1111/J.1475-4754.2008.00434.X
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of spectromicroscopic methods : 4 : artificial aging of model samples of co-precipitates of lead chromate and lead sulfate”. Monico L, Janssens K, Miliani C, van der Snickt G, Brunetti BG, Guidi MC, Radepont M, Cotte M, Analytical chemistry 85, 860 (2013). http://doi.org/10.1021/AC3021592
Abstract: Previous investigations about the darkening of chrome yellow pigments revealed that this form of alteration is attributable to a reduction of the original Cr(VI) to Cr(III), and that the presence of sulfur-containing compounds, most often sulfates, plays a key role during this process. We recently demonstrated that different crystal forms of chrome yellow pigments (PbCrO4 and PbCr1xSxO4) are present in paintings by Vincent van Gogh. In the present work, we show how both the chemical composition and the crystalline structure of lead chromate-based pigments influence their stability. For this purpose, oil model samples made with in-house synthesized powders of PbCrO4 and PbCr1xSxO4 were artificially aged and characterized. We observed a profound darkening only for those paint models made with PbCr1xSxO4, rich in SO42 (x ≥ 0.4), and orthorhombic phases (>30 wt %). Cr and S K-edge micro X-ray absorption near edge structure investigations revealed in an unequivocal manner the formation of up to about 60% of Cr(III)-species in the outer layer of the most altered samples; conversely, independent of the paint models chemical composition, no change in the S-oxidation state was observed. Analyses employing UVvisible diffuse reflectance and Fourier transform infrared spectroscopy were performed on unaged and aged model samples in order to obtain additional information on the physicochemical changes induced by the aging treatment.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 49
DOI: 10.1021/AC3021592
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of spectromicroscopic methods : part 5 : effects of nonoriginal surface coatings into the nature and distribution of chromium and sulfur species in chrome yellow paints”. Monico L, Janssens K, Vanmeert F, Cotte M, Brunetti BG, van der Snickt G, Leeuwestein M, Plisson JS, Menu M, Miliani C, Analytical chemistry 86, 10804 (2014). http://doi.org/10.1021/AC502841G
Abstract: The darkening of lead chromate yellow pigments, caused by a reduction of the chromate ions to Cr(III) compounds, is known to affect the appearance of several paintings by Vincent van Gogh. In previous papers of this series, we demonstrated that the darkening is activated by light and depends on the chemical composition and crystalline structure of the pigments. In this work, the results of Part 2 are extended and complemented with a new study aimed at deepening the knowledge of the nature and distribution of Cr and S species at the interface between the chrome yellow paint and the nonoriginal coating layer. For this purpose, three microsamples from two varnished paintings by Van Gogh and a waxed low relief by Gauguin (all originally uncoated) have been examined. Because nonoriginal coatings are often present in artwork by Van Gogh and contemporaries, the understanding of whether or not their application has influenced the morphological and/or physicochemical properties of the chrome yellow paint underneath is relevant in view of the conservation of these masterpieces. In all the samples studied, microscopic X-ray fluorescence (mu-XRF) and X-ray absorption near edge structure (mu-XANES) investigations showed that Cr(III)-based alteration products are present in the form of grains inside the coating (generally enriched of S species) and also homogeneously widespread at the paint surface. The distribution of Cr(III) species may be explained by the mechanical friction caused by the coating application by brush that picked up and redistributed the superficial Cr compounds, likely already present in the reduced state as result of the photodegradation process. The analysis of the XANES profiles allowed us to obtain new insights into the nature of the Cr(III) alteration products, that were identified as sulfate-, oxide-, organo-metal-, and chloride-based compounds. Building upon the knowledge acquired through the examination of original paint samples and from the investigation of aged model paints in the last Part 4 paper, in this study we aim to characterize a possible relation between the chemical composition of the coating and the chrome yellow degradation pathways by studying photochemically aged model samples covered with a dammar varnish contaminated with sulfide and sulfate salts. Cr speciation results did not show any evidence of the active role of the varnish and added S species on the reduction process of chrome yellows.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 25
DOI: 10.1021/AC502841G
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods : 2 : original paint layer samples”. Monico L, van der Snickt G, Janssens K, de Nolf W, Miliani C, Dik J, Radepont M, Hendriks E, Geldof M, Cotte M, Analytical chemistry 83, 1224 (2011). http://doi.org/10.1021/AC1025122
Abstract: The darkening of the original yellow areas painted with the chrome yellow pigment (PbCrO4, PbCrO4·xPbSO4, or PbCrO4·xPbO) is a phenomenon widely observed on several paintings by Vincent van Gogh, such as the famous different versions of Sunflowers. During our previous investigations on artificially aged model samples of lead chromate, we established for the first time that darkening of chrome yellow is caused by reduction of PbCrO4 to Cr2O3·2H2O (viridian green), likely accompanied by the presence of another Cr(III) compound, such as either Cr2(SO4)3·H2O or (CH3CO2)7Cr3(OH)2 [chromium(III) acetate hydroxide]. In the second part of this work, in order to demonstrate that this reduction phenomenon effectively takes place in real paintings, we study original paint samples from two paintings of V. van Gogh. As with the model samples, in view of the thin superficial alteration layers that are present, high lateral resolution spectroscopic methods that make use of synchrotron radiation (SR), such as microscopic X-ray absorption near edge (μ-XANES) and X-ray fluorescence spectrometry (μ-XRF) were employed. Additionally, μ-Raman and mid-FTIR analyses were carried out to completely characterize the samples. On both paint microsamples, the local presence of reduced Cr was demonstrated by means of μ-XANES point measurements. The presence of Cr(III) was revealed in specific areas, in some cases correlated to the presence of Ba(sulfate) and/or to that of aluminum silicate compounds.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 84
DOI: 10.1021/AC1025122
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“Depth profiling of multilayered systems by means of confocal μ-XRF in the laboratory an at HASYLAB BL L: a comparison”. Alfeld M, Vekemans B, Janssens K, Falkenberg G, Broekaert JAC, Gao N, Gibson D (2007).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Determination of localized Fe2+/Fe3+ ratios in inks of historic documents by means of \mu-XANES”. Proost K, Janssens K, Wagner B, Bulska E, Schreiner M, Nuclear instruments and methods in physics research: B: beam interactions with materials and atoms 213, 723 (2004). http://doi.org/10.1016/S0168-583X(03)01693-8
Abstract: An important part of the European cultural heritage is composed of hand-written documents. Many of these documents were drawn up with iron-gall ink. This type of ink present a serious conservation problem, as it slowly oxidizes ('burns') the paper it is written on, thereby gradually disintegrating the historic document. Acid hydrolysis of the cellulose and/or the oxidation of organic compounds promoted by radical intermediates that are formed due to the presence of Fe2+ ions are considered to be the cause of the disintegration. mu-XANES measurements were performed with a lateral resolution of 30-50 mum in order to determine the local Fe2+/Fe3+ ratio in 19th C. documents from the Austrian National Archives and fragments of 16th C documents from the Polish National Library. In the 19th C documents, no significant amount of Fe2+ was detected. On the other hand, in the 16th C fragments, significant amounts of Fe2+ and appreciable differences in distribution of Fe2+ and Fe3+ within individual letters/ink stains were observed. (C) 2003 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.109
DOI: 10.1016/S0168-583X(03)01693-8
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“Determination of Zn distribution inside edible plants grown on a polluted soil amended with compost by XRF microtomography”. Terzano R, al Chami Z, Vekemans B, Janssens K, Miano T, Ruggiero P (2007).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Development of a new portable X-ray powder diffractometer and its demonstration to on-site analysis of two selected old master paintings from the Rijksmuseum”. Hirayama A, Abe Y, van Loon A, De Keyser N, Noble P, Vanmeert F, Janssens K, Tantrakarn K, Taniguchi K, Nakai I, Microchemical journal 138, 266 (2018). http://doi.org/10.1016/J.MICROC.2018.01.003
Abstract: A portable X-ray powder diffractometer (p-XRD) PT-APXRD III has been developed for onsite analysis of paintings and archaeological samples. By using a Cu anode X-ray tube and a silicon drift diode (SDD) detector, diffraction patterns with a high signalnoise (S/N) ratio can be recorded. The X-ray tube can be operated at a maximum voltage of 60 kV, which makes it possible to simultaneously record X-ray fluorescence spectra up to the high-energy region. The total weight of this instrument is 16 kg, which can be carried anywhere and the goniometer unit (5.6 kg) can be placed on a tripod for analysis of mural paintings. We brought the instrument to the Rijksmuseum in the Netherlands to examine its applicability for the analysis of oil paintings. We successfully analyzed two seventeenthcentury oil paintings by Johannes Vermeer and Jan Davidsz de Heem (copy after). Ultramarine blue, leadtin yellow type I, and Naples yellow were identified from the diffraction patterns, demonstrating the high practicality of this instrument. Furthermore, it was found from the SEM-EDX analysis of a paint cross section that the yellow pigment was applied in separate layers rather than being mixed. This diffractometer will be commercially available in the near future and will have many applications in the field of material analysis. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.034
Times cited: 2
DOI: 10.1016/J.MICROC.2018.01.003
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“Digitally reconstructing Van Gogh's Field with Irises near Arles. Part 2: Pigment concentration maps”. Kirchner E, van der Lans I, Ligterink F, Geldof M, Gaibor ANP, Hendriks E, Janssens K, Delaney J, Color research and application 43, 158 (2018). http://doi.org/10.1002/COL.22164
Abstract: Colors in many paintings of great art historical value have changed over time, due to the combined effects of natural ageing, accumulated surface grime, and materials added during later conservation treatments. The physical restoration of the colors in such paintings is not possible. This article describes one part of work done to digitally restore the colors of Van Gogh's painting Field with Irises near Arles, dating from May 1888. We have used multispectral reflectance data to estimate absorption K and backscattering S parameters of Kubelka-Munk 2-constant theory. This was done for all 13 pigments known to have been used by Van Gogh in this painting, and based on this the concentration maps for each of these pigments were calculated. We validated the calculated concentration maps in several ways. For some pigments, we were able to predict spots on the painting where the pigment is expected to occur in unmixed form based on visual examination. For several other pigments, the concentration maps could be shown to agree with XRF data. Finally, for some other pigments the concentration maps were supported by additional evidence from microscopic examinations, remarks in Van Gogh's letters and from early color reproductions. For the 1.7 million pixels for which multispectral data is available, the average color difference between the calculated and measured spectral reflectance curves is CIEDE2000 = 1.05. This further confirms that the Kubelka-Munk calculations are well suited to describe the variety of spectral reflectance on the painting.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 0.798
Times cited: 4
DOI: 10.1002/COL.22164
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“Disclosing the binding medium effects and the pigment solubility in the (photo)reduction process of chrome yellows (PbCrO4/PbCr1-xSxO4)”. Monico L, Sorace L, Cotte M, de Nolf W, Janssens K, Romani A, Miliani C, ACS Omega 4, 6607 (2019). http://doi.org/10.1021/ACSOMEGA.8B03669
Abstract: The darkening due to chemical alteration of chrome yellows (PbCrO4/PbCr1-xSxO4) is a phenomenon threatening a large number of 19th-20th century paintings, including the Amsterdam Sunflowers by Vincent van Gogh. Our earlier studies have proven that the alteration is due to a Cr(VI) -> Cr(III) reduction with Cr(V)-species that are formed as long-lived intermediates and that bCr(1-x)S(x)O(4) (0 < x <= 0.8) types undergo reduction more readily than monoclinic, S-free, PbCrO4. In this context, there is still lack of knowledge about the effects of the chemical properties of the binding medium (i.e., chemical composition and drying process) and the solubility of chrome yellows on the overall reduction pathways. Here, we study a series of naturally and photochemically aged mock-up paints prepared by mixing chrome yellow powders (PbCrO4/PbCr0.2S0.8O4) with either linseed oil or a water-based acrylic emulsion as the binding medium. Equivalent paints made up of the highly soluble K2CrO4 were also investigated and used as benchmarks to provide a more in-depth understanding of the influence of the solubility on the chromate reduction pathways in the two different binders. A combination of synchrotron radiation-based Cr K-edge X-ray absorption near edge structure (XANES), electron paramagnetic resonance (EPR), and UV-Visible spectroscopy measurements shows that: (1) the Cr(VI) reduction results from the interaction between the pigment and the binder; (2) the process is more significant in oil, giving rise to Cr(V)- and Cr(III)-species as well as oxidized organic compounds; (3) the lightfastness of the chrome yellow pigment is enhanced in the acrylic binder; and (4) the tendency toward chromium reduction increases with increasing solubility of the pigment. Based on our findings, we propose a scheme for the mechanism of the (photo)reduction process of chrome yellows in the oil and acrylic binder. Overall, our results provide new insights into the factors driving the degradation of lead chromate-based paints in artworks and contribute to the development of strategies for preserving them over time.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 4
DOI: 10.1021/ACSOMEGA.8B03669
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“Echt of namaak? Venetiaans glas uit het oude Antwerpen”. de Raedt I, Janssens K, Veeckman J, De wetenschappelijke bibliotheek 67, 58 (1999)
Keywords: A3 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Editorial”. Janssens K, (2003)
Keywords: P3 Proceeding; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Efficiency of applying ammonium oxalate for protection of monumental limestone by poultice, immersion and brushing methods”. Mudronja D, Vanmeert F, Hellemans K, Fazinic S, Janssens K, Tibljas D, Rogosic M, Jakovljevic S, Applied physics A : materials science &, processing 111, 109 (2013). http://doi.org/10.1007/S00339-012-7365-9
Abstract: Samples of cretaceous limestone have been treated with three application methods (poultice, immersion and brushing) using different concentrations of ammonium oxalate solution (AmOx) and varying treatment time in order to test the efficiency of surface and in-depth formation of a protective layer of calcium oxalate (CaOx). Synchrotron-based microanalytical techniques (SR-mu XRD with 12.5 mu mx7.5 mu m (HxV) probe size, SR-mu FTIR with 10 mu mx10 mu m and 8 mu mx20 mu m probe sizes) and laboratory mu FTIR, XRD and SEM have been employed for analysis of the treated samples. Synchrotron-based techniques showed variations in the CaOx distribution along the surface on a micrometer scale. All treatments resulted in the development of a CaOx layer with a maximum thickness of approximately 40 mu m. Application by the brushing method with 10 1-min applications with 5-min breaks during one hour showed a development of the calcium oxalate layer equivalent to the poultice treatment taking 10 h. This treatment could be preferred for large marble or limestone surfaces where poultice usage is economically not feasible.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.455
Times cited: 13
DOI: 10.1007/S00339-012-7365-9
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“Electrochemical photodegradation study of semiconductor pigments : influence of environmental parameters”. Anaf W, Trashin S, Schalm O, van Dorp D, Janssens K, De Wael K, Analytical chemistry 86, 9742 (2014). http://doi.org/10.1021/AC502303Z
Abstract: Chemical transformations in paintings often induce discolorations, disturbing the appearance of the image. For an appropriate conservation of such valuable and irreplaceable heritage objects, it is important to have a good know-how on the degradation processes of the (historical) materials: which pigments have been discolored, what are the responsible processes, and which (environmental) conditions have the highest impact on the pigment degradation and should be mitigated. Pigment degradation is already widely studied, either by analyzing historical samples or by accelerated weathering experiments on dummies. However, in historic samples several processes may have taken place, increasing the complexity of the current state, while aging experiments are time-consuming due to the often extended aging period. An alternative method is proposed for a fast monitoring of degradation processes of semiconductor pigments, using an electrochemical setup mimicking the real environment and allowing the identification of harmful environmental parameters for each pigment. Examples are given for the pigments cadmium yellow (CdS) and vermilion (α-HgS).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
Impact Factor: 6.32
Times cited: 18
DOI: 10.1021/AC502303Z
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“The elemental composition of airborne particulate matter in the Atacama desert, Chile”. Rojas CM, Figueroa L, Janssens KH, Van Espen PE, Adams FC, Van Grieken RE, The science of the total environment 91, 251 (1990). http://doi.org/10.1016/0048-9697(90)90302-B
Abstract: Air particulate samples were collected at Chapiquiña near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/0048-9697(90)90302-B
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“Elemental compositions of comet 81P/Wild 2 samples collected by Stardust”. Flynn GJ, Janssens K, Vekemans B, [et al], Science 314, 1731 (2006). http://doi.org/10.1126/SCIENCE.1136141
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 37.205
Times cited: 174
DOI: 10.1126/SCIENCE.1136141
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“Enhanced transmission versus localization of a light pulse by a subwavelength metal slit”. Kukhlevsky SV, Mechler M, Csapo L, Janssens K, Samek O, Physical review : B : condensed matter and materials physics 70, 195428 (2004). http://doi.org/10.1103/PHYSREVB.70.195428
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.836
Times cited: 17
DOI: 10.1103/PHYSREVB.70.195428
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“Estimation of relative Fe2+ and Fe3+ contents of original manuscript fragments by means of μ-XANES and Mössbauer spectrometry”. Janssens K, Vekemans B, Rouchon-Quillet V (2005).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Euroanalysis 14: the European Conference on Analytical Chemistry”. Janssens K, van Espen P, Van 't dack L, Analytical and bioanalytical chemistry 391, 1107 (2008). http://doi.org/10.1007/S00216-008-2114-9
Keywords: Editorial; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
Impact Factor: 3.431
DOI: 10.1007/S00216-008-2114-9
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“Evaluation and calibration of micro-XRF data”. Janssens K, Vincze L, Vekemans B page 155 (2000).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Evaluation of a Monte Carlo simulation for EDXRF spectrometers at beamline BW5, HASYLAB”. Vincze L, Vekemans B, Janssens K, Adams F, Lippmann T, HASYLAB Jahresbericht 1997 1, 1043 (1998)
Keywords: A3 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Evaluation of energy-dispersive x-ray-spectra with the aid of expert systems”. Janssens K, van Espen P, Analytica chimica acta 191, 169 (1986). http://doi.org/10.1016/S0003-2670(00)86306-0
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
DOI: 10.1016/S0003-2670(00)86306-0
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“Evaluation of manganese-bodies removal in historical stained glass windows via SR-\mu-XANES/XRF and SR-\mu-CT”. Cagno S, Nuyts G, Bugani S, De Vis K, Schalm O, Caen J, Helfen L, Cotte M, Reischig P, Janssens K, Journal of analytical atomic spectrometry 26, 2442 (2011). http://doi.org/10.1039/C1JA10204D
Abstract: The speed and effectiveness of a conservation treatment used for stained glass windows have been investigated. Dark-coloured Mn-rich stains can be found in the alteration layer of ancient glass artefacts and cause the surface to turn brown/black: this phenomenon is known as Mn-browning or Mn-staining. While in glass manganese is present in the +II or +III oxidation states, in the Mn-rich bodies, manganese is in a higher oxidation state (+IV). In restoration practice, mildly reducing solutions are employed to eliminate the dark colour and restore the clear appearance of the glass. In this paper the effectiveness and side effects of the use of hydroxylamine hydrochloride for this purpose are assessed. Archaeological fragments of stained glass windows, dated to the 14th century and originating from Sidney Sussex College, Cambridge (UK), were examined by means of synchrotron radiation (SR) based microscopic X-ray Absorption Near-Edge Spectroscopy (μ-XANES) and microscopic X-Ray Fluorescence (μ-XRF) and with high resolution computed absorption tomography (μ-CT) before, during and after the treatment. The monitoring of the glass fragments during the treatment allows us to better understand the manner in which the process unfolds and its kinetics. The results obtained reveal that the hydroxylamine hydrochloride treatment is effective, but also that it has a number of unwanted side effects. These findings are useful for optimizing the time and other modalities of the Mn-reducing treatment as well as minimizing its unwanted results.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 17
DOI: 10.1039/C1JA10204D
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“Evaluation of polycapillary lenses as focussing elements in sub-mm XRF analysis of artistic objects”. Vekemans B, Janssens K, Adams F, Andong L, He Y, Yiming Y page 278 (1998).
Keywords: H3 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Evaluation of polyvinyl alcohol–borax/agarose (PVA–B/AG) blend hydrogels for removal of deteriorated consolidants from ancient Egyptian wall paintings”. Al-Emam E, Motawea AG, Janssens K, Caen J, Heritage science 7, 22 (2019). http://doi.org/10.1186/S40494-019-0264-Z
Abstract: This study concerns the assessment of a new polyvinyl alcohol–borax/agarose blend hydrogel (PVA–B/AG) tailored for the conservation of ancient Egyptian wall paintings. The increasing problems of deteriorated consolidants affecting ancient wall paintings have attracted the interest of conservation scientists in the last 20 years. The ability of a new blend for removing aged Paraloid® B-72 layers from painted stone and plaster samples has been evaluated. The hydrogel blend was used to expose the aged Paraloid in a controlled manner to six different cleaning system (CS). CS1–CS4 consist of solvents or solvent mixtures; CS5 and CS6 are nanostructured fluids (NSFs). The evaluation of the removal process was carried out by quantitative and qualitative methods, namely, visual examination, 3D microscopy, contact angle and colorimetric measurements and by Fourier transform infra-red spectrometry in reflectance mode. The results showed that the PVA–B/AG blend hydrogel, loaded with specific cleaning systems, was able to remove deteriorated B-72 and allowed to restore the painted surface to a state close to the original one. The PVA–B/AG blend showed good workability, permitting it to be easily cut, shaped, applied and removed. It could also be verified by means of different investigation methods that the blend left no detectable residues. As a final realistic check of the method, the PVA–B/AG hydrogel loaded with the best functioning cleaning system (CS3) was used to remove an aged consolidant layer from an ancient Egyptian wall painting.
Keywords: A1 Journal article; Engineering sciences. Technology; Art; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
Times cited: 2
DOI: 10.1186/S40494-019-0264-Z
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“Evaluation of the ArmstrongBuseck correction for automated electron probe X-ray microanalysis of particles”. Storms HM, Janssens KH, Török SB, Van Grieken RE, X-ray spectrometry 18, 45 (1989). http://doi.org/10.1002/XRS.1300180203
Abstract: The ArmstrongBuseck correction for absorption effects in electron probe x-ray microanalysis of particles considers seven specific particle shapes, and for these geometries exact correction equations are used. This procedure implies that the analyst has to associate the particle to be analysed with a certain particle type; an arbitrary relative thickness is sometimes assumed. A theoretical study was made of this absorption correction as a function of the particle composition, type and thickness for micrometre-sized particles. It appears that a correct choice of the particle type is critical. However, when the analytical results are normalized to 100%, the differences between the models are much less pronounced, and it is justified to assume a spherical model in all cases.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1002/XRS.1300180203
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“Evidence for degradation of the chrome yellows in Van Gogh's sunflowers : a study using noninvasive in situ methods and synchrotron-radiation-based x-ray techniques”. Monico L, Janssens K, Hendriks E, Vanmeert F, van der Snickt G, Cotte M, Falkenberg G, Brunetti BG, Miliani C, Angewandte Chemie: international edition in English 54, 13923 (2015). http://doi.org/10.1002/ANIE.201505840
Abstract: This paper presents firm evidence for the chemical alteration of chrome yellow pigments in Van Gogh's Sunflowers (Van Gogh Museum, Amsterdam). Noninvasive in situ spectroscopic analysis at several spots on the painting, combined with synchrotron-radiation-based X-ray investigations of two microsamples, revealed the presence of different types of chrome yellow used by Van Gogh, including the lightfast PbCrO4 and the sulfur-rich PbCr1-xSxO4 (x approximate to 0.5) variety that is known for its high propensity to undergo photoinduced reduction. The products of this degradation process, i.e., Cr-III compounds, were found at the interface between the paint and the varnish. Selected locations of the painting with the highest risk of color modification by chemical deterioration of chrome yellow are identified, thus calling for careful monitoring in the future.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 11.994
Times cited: 24
DOI: 10.1002/ANIE.201505840
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“Evidence of early medieval soda ash glass in the archaeological site of San Genesio (Tuscany)”. Cagno S, Favaretto L, Mendera M, Izmer A, Vanhaecke F, Janssens K, Journal of archaeological science 39, 1540 (2012). http://doi.org/10.1016/J.JAS.2011.12.031
Abstract: The early medieval period marks an important turning point in the history of glassmaking, since it comprises the transition period between the mineral-based silica-soda-lime glass of the Roman tradition and the plant ash-based glass. With the aim of expanding the knowledge on the glass recipes and technologies of this period, 37 glass samples were analyzed, originating from the archaeological excavations of San Genesio (Tuscany) and dated from the fourth to the eleventh century. The major and minor element concentrations were measured with SEM-EDX, while the trace elements were quantified with LA-ICP-MS. The results were compared with published compositions of glass samples of similar age in order to highlight differences and similarities. The results offer a very interesting view on the glass circulation in the religious/residential/manufacturing center of San Genesio in the early medieval period. Most of the glass has a typical late-Roman composition, but some glass fragments are identified as soda ash glass. These are among the earliest medieval ash-fluxed glasses ever found in the Italian peninsula. (C) 2011 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Philosophy; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.602
Times cited: 24
DOI: 10.1016/J.JAS.2011.12.031
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“Examination of historical paintings by state-of-the-art hyperspectral imaging methods : from scanning infra-red spectroscopy to computed X-ray laminography”. Legrand S, Vanmeert F, van der Snickt G, Alfeld M, de Nolf W, Dik J, Janssens K, Heritage science 2, 13 (2014). http://doi.org/10.1186/2050-7445-2-13
Abstract: The development of advanced methods for non-destructive selective imaging of painted works of art at the macroscopic level based on radiation in the X-ray and infrared range of the electromagnetic spectrum are concisely reviewed. Such methods allow to either record depth-selective, element-selective or species-selective images of entire paintings. Camera-based full field methods (that record the image data in parallel) can be discerned next to scanning methods (that build up distributions in a sequential manner by scanning a beam of radiation over the surface of an artefact). Six methods are discussed: on the one hand, macroscopic X-ray fluorescence and X-ray diffraction imaging and X-ray laminography and on the other hand macroscopic Mid and Near Infrared hyper- and full spectral imaging and Optical Coherence Tomography. These methods can be considered to be improved versions of the well-established imaging methods employed worldwide for examination of paintings, i.e., X-ray radiography and Infrared reflectography. Possibilities and limitations of these new imaging techniques are outlined.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1186/2050-7445-2-13
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