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Application of synchrotron infrared radiation in the study of organic coatings in cross-sections
(2008)
Nondestructive analyses of medieval reverse paintings on glass revealed the same dyes and pigments customarily used in panel paintings. However, there is one exception: the black colorant is not a carbon-based pigment, but black enamel. In this respect, the stylistic as well as the technical influence of stained glass artwork can clearly be seen on reverse paintings on glass. However, there is a crucial difference: in reverse paintings, the black enamel is not fired onto the glass but painted (cold painting). Additional analyses confirmed these findings. Based on these results, the art form "reverse painting on glass" has technically to be characterized as a mixture of "stained glass" and "panel painting" that nonetheless develops into a genre of its own.
In this work, the applicability of a new 3D micro X-ray fluorescence (3D Micro-XRF) laboratory spectrometer for the investigation of historical glass objects is demonstrated. The non-destructiveness of the technique and the possibility to measure three-dimensionally resolved fluorescence renders this technique into a suitable tool for the analysis of cultural heritage objects. Although absorption and resolution effects complicate qualitative analysis of the data, layered structures can be distinguished from homogeneous samples without the need for full quantification. Different manufacturing techniques were studied in this work with the help of hand-made reference samples. With the gained knowledge it could be shown for the investigated historical glass object, that black enamel as a stained glass contour colour was used in a cold painting. The object was not fired after the application of the black enamel, but instead the adhesion of the paint was solely provided through organic binding agents and the backing with metal foils. Thus, for the manufacturing of the object, a mixture of cold painting technique with a stained glass color was used. Quantitative measurements with a 3D Micro-XRF setup at the Berlin synchrotron BESSY II confirm the assumptions drawn on the basis of the qualitative investigation with the 3D Micro-XRF spectrometer with X-ray tube excitation.
Our standard protocol for the characterisation of writing materials within advanced manuscript studies has been successfully used to investigate manuscripts written with a pure ink on a homogeneous writing surface. However, this protocol is inadequate for analysing documents penned in mixed inks. We present here the advantages and limitations of the improved version of the protocol, which now includes imaging further into the infrared region (1100−1700 nm).
Confronted with indications that the SNML could be a forgery, we reviewed data from our previous analyses again and supplemented it with additional readings. Again, we were short of time. During the first measurement campaign we employed X-ray fluorescence analysis to identify specific trace elements and thereby characterize different writing and drawing materials. In the new measurement campaign, we once again carried out an extensive X-ray fluorescence analysis. In addition, this time we also employed reflection infrared spectroscopy and confocal microscopy.
As with earlier measurement campaigns, we were determined not to take samples. Throughout the process, we have continued to regard the object in question as unique, and as such not to he physically altered in any way. Throughout the analysis, however, it has been clear that non-destructive testing provides less comprehensive results than methods that require testing physical samples. The examinations described below were carried out not only on the SNML, but also on reference objects. The most important of these in this framework was the SN Graz, which is generally accepted as authentic. The following illustrates the results of the analysis in detail.
Fe K-edge XANES measurements were performed to determine the oxidation state of iron in iron gall inks. These data are used to investigate the relationship between the Fe oxidation state and ink corrosion in historical manuscripts. The oxidation state is determined using the pre-edge based on a general variation trend that was derived from model compounds and validated here independently on a suite of samples with known oxidation state and Fe in octahedral coordination (i.e. similar to Fe in gall ink). As long as suitable references for the pure ferric and ferrous state of iron gall inks cannot be pointed out, the analysis of the pre-edge of the Fe K-edge represents the only way to acquire absolute values for the Fe oxidation state (Fe3+/Fetot) with spatial resolution for this usually non-crystalline compound. Fe3+/Fetot values for the ink samples vary between ca. 0.7 and 1.0. Spatially resolved analyses performed across ink strokes of various historical manuscripts as well as newly made samples did not reveal any systematic spatial dependence. On average, historical samples that were exposed to conservation treatments show a more oxidized state. However, the measurements demonstrate explicitly that the exposure to X-rays during the XANES acquisition affects the oxidation state of Fe in most iron gall inks.
The Nepal-German Manuscript Preservation Project (NGMPP) microfilmed two sets of the rNying margyud 'bum: in 1989 the set stored in the National Archives in Kathmandu (NAK) and in 1992 another set during an expedition to Nubri, Samagaon. Both microfilming were carried out under the local director of the Nepal Research Centre (NRC) in Kathmandu, and who has also discussed the two (and other) rNying ma rgyud 'bum sets on several occasions.2 The NAK and Nubri rNying ma rgyud 'bum sets were extensively studied and catalogued (Almogi) within the framework of the Tibetology sub-project "The Manuscript Collections of supervision of Franz-Karl Ehrhard, who was at the time the the Ancient Tantras (rNying ma rgyud 'bum): An Examination of Variance," conducted at the Researcher Group "Manuscript Cultures in Asia and Africa," University of Hamburg (2008-2011).
This article presents the findings resulting from the material analysis of several Sanskrit palm-leaf manuscripts from a corpus partly preserved in Nepal, viz. in the National Archives, Kathmandu (NAK), and in the Kaiser Library (KL), which is likewise situated in Kathmandu. The analysis was undertaken in March 2013. The colleagues of the NAK allocated a room in their precincts to us, where we could set up our mobile laboratory, and gave us access to the required manuscripts from their holdings. The officials of the KL, in turn, allowed us to take some of their valuable and ancient manuscripts to the NAK. In this way, we were enabled to conduct multi-instrumental studies on writing materials of great antiquity and interest.
Die naturwissenschaftliche Analyse historischer Materialen ermöglicht die Beantwortung kulturhistorischer Fragestellungen, die mit kunsthistorischen oder archäologischen Ansätzen allein nicht zu leisten sind. In dieser Studie wurden sechs römische Münzen mit unterschiedlich stark ausgeprägten Korrosionsschichten an unbehandelten und polierten Stellen mit vier zerstörungsfreien analytischen Methoden untersucht: Hoch- und Niederenergie Protonen Induzierter Röntgenemission (HE-/PIXE), Synchrotronstrahlungsinduzierte-Röntgenfluoreszenzanalyse (SY-RFA) und Mikro-Röntgenfluoreszenzanalyse (Mikro-RFA) mit einem mobilen Gerät. Aufgrund von Unterschieden in den Messbedingungen und dem Einfluss der Patina-Schichten auf diese ergaben sich nur für wenige Elemente Übereinstimmungen in den quantitativen Daten. Zur Validierung zukünftiger Messkampagnen mit verschiedenen Methoden sind daher Vergleichstudien unerlässlich.