Showing papers by "Ina Reiche published in 2007"

3D Micro-PIXE at atmospheric pressure: A new tool for the investigation of art and archaeological objects

Abstract: The paper describes a novel experiment characterized by the development of a confocal geometry in an external Micro-PIXE set-up. The position of X-ray optics in front of the X-ray detector and its proper alignment with respect to the proton micro-beam focus provided the possibility of carrying out 3D Micro-PIXE analysis. As a first application, depth intensity profiles of the major elements that compose the patina layer of a quaternary bronze alloy were measured. A simulation approach of the 3D Micro-PIXE data deduced elemental concentration profiles in rather good agreement with corresponding results obtained by electron probe micro-analysis from a cross-sectioned patina sample. With its non-destructive and depth-resolving properties, as well as its feasibility in atmospheric pressure, 3D Micro-PIXE seems especially suited for investigations in the field of cultural heritage.

Microanalysis and synthesis of calcite. Growth mechanisms on prehistoric paintings in the large cave, Arcy-sur-Cure (Yonne, France)

Abstract: The formation of subsequent layers of calcium carbonate (CaCO3) in karst caves is a well known phenomenon particularly observed on the prehistoric paintings at the Large cave (“Grande Grotte”) of Arcy-sur-Cure, in France. About forty natural samples coming from the Large cave were already investigated in a previous work and classified as a function of their crystal morphology, fabric, composition and appearance. The presence of at least two calcite types was revealed on the walls: translucent and opaque white or grey calcites. The latter opaque calcites obstruct completely the paintings. The formation of these different calcites depends on various geochemical and geophysical parameters and could also be influenced by biotic processes. Questions remain about formation mechanisms leading to different calcite types and in particular about the role of microorganisms as well as interactions between prehistoric paint layers and calcite layers. Additional natural calcites were studied in order to confirm the first classification. Various syntheses of abiotic calcite were performed to study the influence of environmental parameters on calcite growth. Moreover, several series of biotic calcite were synthesised in a specific medium with two bacteria isolated from the cave in order to test their calcifying properties. All natural and synthetic samples were analysed using complementary microanalytical laboratory techniques. Micro-XRF and XANES based on synchrotron radiation also enabled more detailed distinguishing different minerals within the complex biotic and abiotic mixtures and layered synthetic samples at microscopic scale. Comparison of natural and synthetic samples gives more detailed insights into the formation mechanisms of the different calcite types found in the “Grande Grotte” and allows proposing an adapted conservation strategy of its prehistoric paintings.

Biotic versus abiotic calcite formation on prehistoric cave paintings: the Arcy-sur-Cure ‘Grande Grotte' (Yonne, France) case

Abstract: The ‘Grande Grotte' cave at Arcy-sur-Cure (Yonne, France) with its prehistoric paintings shows important calcite concretions. Two types of calcite have been observed on the wall: translucent yellowish layers and opaque white or grey layers that completely obstruct the paintings. Other calcite types are present in the lakes of the cave (floating calcite rafts at the surface of the lake and soft calcite at the bottom of the lake). The morphology of the different calcites was observed at different scales by optical microscopy with normal and polarized light, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elemental composition was measured by using particle-induced X-ray emission (micro-PIXE) and the structure by X-ray diffraction (XRD), infrared (FT-IR) and Raman spectroscopy. The bacterial diversity and its role in calcite formation were assessed by culture and 16S-SSCP in order to distinguish and to assess various abiotic and biotic formation mechanisms. The investigation of calcite characteristics enables conclusions on the formation mechanism and on a biotic or abiotic origin of the calcites. The change of calcite types on the walls reveals changes of the environmental cave parameters. In addition, interactions of calcites with the prehistoric paint layer could be evaluated.

Les matériaux osseux archéologiques : Des biomatériaux nanocomposites complexes

Abstract: De nombreuses interpretations archeologiques sont fondees sur des analyses isotopiques et des elements traces des vestiges osseux. En effet, l'os et la dent enregistrent en tant que biomateriaux les conditions de vie (regimes alimentaires, climat, mode d'habitat) dans leur composition chimique et leur structure. Cependant, les vestiges anciens sont souvent soumis a de nombreux phenomenes d'alteration dus a l'interaction avec l'environnement sedimentaire. Le but de ce travail est de reveler les mecanismes d'alteration des materiaux osseux anciens lors de leur sejour dans les sols et de mettre en evidence des modifications induites par un chauffage. La structure composite de ces materiaux necessite le recours a une methodologie analytique de haute resolution couplant l'observation a differentes echelles a l'analyse chimique et structurale. Les connaissances acquises sur les mecanismes physico-chimiques d'alteration des materiaux osseux et les modifications induites par un chauffage ont permis d'elucider un phenomene controverse depuis longtemps : l'apparition de la couleur bleue lors du chauffage de vestiges osseux fossiles ; ces materiaux osseux nommes turquoises osseuses ou odontolites ont ete utilises comme pierres semi-precieuses pour orner des objets d'art au Moyen-Âge. La methodologie etablie peut maintenant etre appliquee a d'autres problematiques archeologiques telles que l'utilisation du feu par les populations prehistoriques et la differenciation des feux naturels et volontaires. Dans le futur, ces recherches seront etendues a la mise en place des strategies de conservation-restauration des vestiges osseux anciens.

SY-XRF study of Hans Baldung Grien silverpoint drawings and the silver stylus from the ‘Karlsruhe sketchbook’

Abstract: We performed spatially resolved synchrotron-induced x-ray fluorescence analyses (SY-XRF) of five silverpoint drawings from the famous 'Karlsruhe sketchbook' and a silverpoint, which is assumed to be an original one used by the Renaissance artist Hans Baldung Grien (1484-1545) himself. The silverpoint, one out of a very small number of ancient styli conserved nowadays, is fixed on the so-called 'Karlsruhe sketchbook'. Measurements were executed at the FLUO-TOPO beamline at the electron storage ring ANKA. It has been shown, that SY-XRF at this beamline is nondestructive and sensitive enough for the analysis of minor and major elements in the silver strokes. This study provides new insights into this graphical technique and ancient drawing instruments: results are that three drawings have been created with a common type of silverpoint containing about (10.4 ± 0.7) wt% of Cu. In all the cases, Hg at a 10% level by weight was identified in the strokes. Presence of Hg is not due to the original silver alloy, but is a result of a general alteration phenomenon of silverpoint drawings. This fact is confirmed by the analysis of the original silverpoint, which contains only small traces of Hg. The result for the copper content of the silverpoint (10.4 ± 1.7) wt% is in good agreement with that of these three drawings. It is supposable that the silverpoint found attached today served for the creation of the corresponding drawings. Moreover, the graphical technique of Baldung is found to be continual over three decades. Only one very late drawing dated to 1543 was probably realized with another silverpoint, containing about 3 wt% of Cu. This difference in the chemical composition of drawings from the late period might be used as a more precise dating indicator of Baldung drawings that are not clearly attributed to a certain period.