A Note on the Analysis of Gilded Metal Embroidery Threads

The chemical composition of metal decorations in old textile objects must be known in order to enable the best possible cleaning, conservation, care and storage of this priceless part of our cultural heritage. The currently used technique, scanning electron microscopy/energy.-dispersive X-ray analysis (SEM/EDS), however, may sometimes give erroneous results for gilded metal threads. The reason is that a small drop- shaped volume rather than a spot is analysed, so that when trying to analyse a thin gold layer (often <1μm), part of the underlying bulk metal will unintentionally be included in this volume, thus giving an apparent and too low gold concentration. Other sources of error are defects in the gold layer, non-uniform thickness, impurities, microcracks, intra-atomic exchange due to diffusion processes, contaminations and corrosion products on the surface. Strategies to overcome some of these difficulties are suggested, and the use of Auger electron spectroscopy (AES) is exemplified.