Colorando Auro: contribution to the understanding of a medieval recipe to colour gilded silver plates

The colour of gildings can be modified by many artistic techniques. This article refers to the possibility of a specific chemical treatment to change the colour of gildings. The model samples—gilded silver plate, the mixture and the application of a medieval recipe based on ancient writings from Theophilius and Cellini have been described. We propose a strategy to identify the chemical processes involved in the change of colour of the metallic surface through the advanced study of these model samples. Synchrotron X-ray photoelectron spectroscopy and X-ray absorption spectroscopy were carried out both on the gilding with and without the application of the treatment with the aim to understand the chemical reactions occurring during the treatment.