Gold Leaf Alloys Specifically Designed for Conservation

International audienceModern conservation ethics requires that materials and products used for restoration should be reversible, identifiable and traceable. While great improvements have been made in most artistic fields, conservation of gilded objects has yet to develop better solutions to this problem. Leaf gilding restoration on museum objects is often performed with gold leaf substitutes like mica powders or watercolours, although the result can be unsatisfactory in terms of aesthetics and ageing. Gaps in the gilded surfaces are still frequently covered with new gold leaf, which is neither traceable nor reversible. This technique makes it difficult, if not impossible, to differentiate the restored gilding from the original, because the composition and thickness of the new leaf may be indistinguishable from the original authentic gilding or re-gilding. A research program has been developed by the Centre de Recherche et de Restauration des Musées de France (C2RMF) in collaboration with the Dauvet goldbeater society to elaborate on new gold alloys containing small amounts of chemical markers, which could be easily detected by commonly available analytical techniques. This paper presents the development of such alloys, including choice of chemical markers, elaboration process and thermo-mechanical treatments to be applied during the fabrication of foil and leaf. The new leaf needs to have similar appearance in colour and thickness to the authentic gilding. The metal leaf was tested on various substrates and analysed with ion beam analyses using the C2RMF particle accelerator by particle induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) to validate the pXRF analysis performed. This paper also addresses the implications of the proposed processes with respect to conservation-restoration ethics, practical beating and gilding workshop procedures