Study of the conservation problems of the archaeological gilded metals from the Islamic site of Qalat Rabah

This study is based on the research of a set of gilt metals recovered from the site of Qalat Rabah, an ancient Islamic city from Spain. Their conservation are always difficult to face, especially when dealing with aggressive and polluted environments, weathering or inadequate interventions. The conservation of these gilded objects turns out to be much more difficult when they have been buried for centuries and recovered by means of an archaeological excavation. Several archaeometric techniques have been employed to analyse the corrosion crusts. We have obtained the data preferably from non destructive techniques such as particle induced X-ray emission (PIXE), Rutherford backscattering (RBS) and scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDAX). Finally a metallographic study has been carried out using detached fragments of these gilded objects. Analytical evidence points to the employment of a mercury based gilding technology. To sum up, this paper offers the latest results of our Dorados Programme, which combines the study of three topics: the manufacturing technology, the degradation processes of the gilded layer and improved conservation techniques for their cleaning.