Manfred Schreiner

X‐ray fluorescence spectrometry in art and archaeology

This paper presents examples of analyses by x-ray fluorescence (XRF) spectrometry in art and archaeology, including pigments in paint layers and illuminated manusripts, of iridescent glasses and of medieval coins. Theoretical aspects of information depths and shielding effects in layered materials are discussed. Element maps were experimentally obtained by a specially designed x-ray spectrometer (1 × 1 mm pixel resolution) and by electron-excited XRF (electron microprobe). Copyright

X-rays in art and archaeology: An overview

An overview of the techniques used in art and archaeology is presented and the applicability of X-ray radiography, X-ray fluorescence (XRF) and X-ray diffraction analysis (XRD) as a tool for non-destructive investigations of objects of art and archaeology is discussed. X-ray radiography e.g. is a standard technique widely used and accepted by art historians, archaeologists, curators and conservators as this method enables information about the manufacturing process and the condition of an object without “touching” the artifact. XRF and XRD enable a non-destructive determination of the material composition of artifacts and the determination of the crystalline structure of the components too. Air path systems and instruments with the micro-beam of X-ray and synchrotron radiation were applied for the analysis of easel paintings, pigments in paint layers, glass artifacts and coins.

A compact μ-XRF spectrometer for (in situ) analyses of cultural heritage and forensic materials

Abstract A compact, light weight and relatively inexpensive μ-XRF instrument that allows for non-destructive and local analysis of sub-mm samples with minor/trace level sensitivity was developed. Two versions of this prototype instrument exist: a table-top version that can be used in a laboratory environment while for in situ measurements a readily transportable version was constructed. Polycapillary lenses are used to focus the primary X-ray beam down to the level of 70–100 μm in diameter. Relative detection limits of transition elements in biological and glass matrices are situated at the 10–100 ppm level. These instruments are useful for characterization of various materials from the cultural heritage and forensic sector.

Historical pigments: a collection analyzed with X-ray diffraction analysis and X-ray fluorescence analysis in order to create a database☆

Abstract The main objective of this work is the identification of inorganic pigments with X-ray diffraction analysis in combination with X-ray fluorescence analysis (XRF). By using these techniques, differences of specific pigments with identical names but produced by different manufacturers, techniques, or raw materials are revealed. The purity and the chemical compositions of these pigments are tested and the different phases in the diffractograms identified. Measurements with XRF are carried out in order to facilitate the analysis of the diffractograms and to point out differences in the elemental composition of different pigments. The creation of a database of the obtained data and diffractograms is in progress. It will be a collection of the most common and interesting pigments used in art. Furthermore, this database will enable a fast and easy identification of pigments during the restoration and conservation of an object of art.

Characterisation of ancient and art nouveau glass samples by Pb isotopic analysis using laser ablation coupled to a magnetic sector field inductively coupled plasma mass spectrometer (LA-ICP-SF-MS)

LA-ICP-MS was applied for the characterization of historic glass samples by Pb isotope ratios. Laser and ICP-MS parameters were adjusted in order to obtain accurate data with minimum total combined uncertainty and minimum damage to the samples. Moreover, we evaluated mass discrimination correction procedures for these specific samples. No significant laser induced mass bias effects could be observed for glass samples by comparing LA-ICP-MS with pneumatic nebulisation ICP-MS. Iridescent Art Nouveau lead crystal glass samples were analyzed and it could be proved that the material of the single layers originates from different glass sources. The analysis of glass fragments from the archaeological site in Ephesos, Turkey, showed only a low concentration of Pb. Nevertheless, we achieved a successful differentiation of the investigated samples via the Pb isotope ratios whereas multi element pattern did not allow grouping of the data.

Determination of localized Fe2+/Fe3+ ratios in inks of historic documents by means of μ-XANES

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. μ-XANES measurements were performed with a lateral resolution of 30–50 μm 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.

Multianalytical approach to explain the darkening process of hematite pigment in paintings from ancient Pompeii after accelerated weathering experiments

In this paper, recently excavated fresco painting fragments from the House of Marcus Lucretius (Pompeii) and not exposed to the atmosphere since the eruption of the Mount Vesuvius were subjected to a controlled SO2 atmosphere and high relative humidity. These experiments were conducted in order to simulate under accelerated conditions the possible deterioration of the hematite pigment and plaster. The mineralogical transformation of the polychromy and plaster was monitored using mainly Raman spectroscopy, a non-destructive technique, but also infrared spectroscopy (FT-IR) and scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS). After different exposure cycles to SO2, it was confirmed that hematite red pigment (Fe2O3) can be reduced into magnetite (Fe3O4), which provides the darkened colour to the pigment. While Fe(III) from hematite is reduced into Fe(II) or mixed Fe(III) and Fe(II), the SO2 can be oxidized (SO3) and hydrated to experience a subsequent wet deposition (H2SO4 aerosol) causing also the transformation of calcite into gypsum. Finally, it was assessed that high concentrations of SO2 can also cause the sulphation of hematite pigment promoting its transformation into paracoquimbite/coquimbite (Fe2(SO4)3·9H2O). Moreover, in some areas of the deteriorated painting fragments, non-expected iron(II) sulphate and sulphite species were also identified.

Iridescent Art Nouveau glass – IBA and XPS for the characterisation of thin iridescent layers

Abstract The external proton beam of the Tandem accelerator of the Research Centre in Rossendorf/Germany was used to carry out non-destructive particle-induced X-ray emission (PIXE) particle-induced gamma-ray emission (PIGE) and Rutherford backscattering (RBS) measurements simultaneously on Art Nouveau artifacts produced around 1900 by Tiffany/USA and Loetz/Austria. These studies should proof the technology of producing an iridescent layer on a glass surface. By means of the yield ratio Y (Si-K)/ Y (Si-γ) of both characteristic X-radiation (Si-K) and γ-radiation (Si-γ) of the element silicon it could be shown that a thin top layer is present on the glass surface due to the treatment of the heated artifacts (about 500°C) with an alcoholic solution of SnCl 2 [1] . Combined evaluation of the PIXE and RBS spectra resulted in a thickness of 20–300 nm for this top layer. In addition, a transition region between the iridescent layer and the bulk glass was obtained by RUMP simulations. Approximately 80% of the total amount of the Sn were found to be present in this transition layer and only 10–20% in the outermost surface region. XPS studies showed that the outermost layer consists of SnO 2 . The formation of other Sn compounds in the outermost near-surface region based on Sn–Si–O during the manufacturing process can be excluded.

Morpho peleides butterfly wing imprints as structural colour stamp.

This study presents the replication of a color-causing nanostructure based on the upper laminae of numerous cover scales of Morpho peleides butterfly wings and obtained solely by imprinting their upper-wing surfaces. Our results indicate that a simple casting technique using a novel integrated release agent can obtain a large positive replica using negative imprints via Polyvinylsiloxane. The developed method is low-tech and high-yield and is thus substantially easier and less expensive than previous methods. The microstructures were investigated with light microscopy, the nanostructures with both scanning and transmission electron microscopy, and the reflections with UV visible spectrometry. The influence of the release agent and the quality of the master stamp were determined by comparing measurements of the cover-scale sizes and their chromaticity values obtained by their images and with their positive imprints. The master stamp provided multiple positive replicas up to 3 cm(2) in just 1 h with structural coloration effects visible to the naked eye. Thus, the developed method proves the accuracy of the replicated nanostructure and its potential industrial application as a color-producing nanostamp.

The Use of Focussed X-Ray Beams for Non-Destructive Characterization of Historical Materials

In this work, the use of X-ray micro beams for non-destructive characterization of historical, archaeological and artistic materials will be described. Only the use of X-ray micro beams generated in dedicated beam lines of synchrotron storage will be discussed. Attention will be devoted to two methods of analysis:.t-XRF (X-ray fluorescence analysis) [1] and µ-XANES (X-ray absorption near-edge spectroscopy) [2]. The former method allows quantitative trace-level micro-analysis of a variety of materials while the second permits to extract information on the valence of (trace) metals in these materials. µ-XRF may be practised at synchrotron beam lines, where the polarized nature of the radiation can be used advantageously for lowering the scatter background level in the energy-dispersive X-ray spectra, leading to improved detection limits. When suitable focussing devices are employed,.t-XRF measurements can also be performed by means of compact and/or portable laboratory equipment. The latter kind of instrumentation allows for in-situ measurements (for example in a gallery, a museum etc.). In view of the requirement to employ highly monochromatic radiation, tXANES is a method that only can be employed at synchrotron facilities. The use of these methods for characterization of historical glass fragments and handwritten paper documents is briefly described.