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Investigations on 16th to 19th c. Limoges painted enamels by a new mobile spectrometer for Micro X-Ray Fluorescence SpectrometryDr. Heike Bronk (Institut für Anorganische und Analytische Chemie, Technische Universität Berlin) During the past decade X-ray fluorescence spectrometry (XRF) for non-destructive and highly sensitive multi-elemental analysis has been undergoing a considerable and not yet finished technical development. Both the combination of miniaturised low-power X-ray tubes with glass-capillary optics, which are able to generate an intense primary beam in the µm-range, and the development of detectors working without liquid nitrogen meet the demands of archaeometry for portability and high lateral resolution. Within a research project on dating problems of 16th century enamel paintings from Limoges (France) a µ-XRF spectrometer (ArtTAX) was designed which is especially suitable for the determination of glass matrix elements. This system consists of an air-cooled Mo-tube, a polycapillary optics to focus the beam down to a spot size of 80 - 100 µm and a Peltier-cooled Silicon Drift Chamber-detector. Additional helium flow allows the analysis of light elements down to sodium. Sample positioning as well as documentation of the investigated area is done with an integrated CCD camera and frame grabber. The measurement head is fixed on a X,Y,Z-flexible support which can be assembled and dismantled within minutes. Handling, spectroscopic features and first applications on various materials will be presented. ArtTAX is currently under use with-in museum investigations on Limoges painted enamels in German collections. These outstanding objets d`art were created by highly specialised French workshops from the late 15th till the beginning of the 17th century. During the reviving interest in medieval and Renaissance art in historism this lost art was "rediscovered" and 19th century replicas were often sold as genuine. A severe judgement of their authenticity is often difficult on the stylistic basis alone. Especially the nature of the polychrome or grisaille enamel fluxes with its basic composition, colouring metals and opacifiers as well as their content of impurities can give valuable additional information on the dating of pieces in question as well as to characterise specific attributes of certain enameller workshops. |
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