In the Middle Ages goldsmiths and craftsmen possessed a number of recipes for changing the color and the hue of gold and gilded objects. A recent article presents an overview of these techniques.
De Colorando Auro: Experiments and literature study of medieval colouring recipes on gilded plates
By Amandine Caroline Crabbé, Alessandra Giumlia-Mair, Helena J. M. Wouters, Herman Terryn, Isabelle Vandendael
In: Studies in Conservation. Advanced articles 2015
Metal craftsmen seem to have been intrigued by the fact that the colour of metal could be changed in very many ways. The most obvious solution was of course to change the composition of the gold alloy. But in case of gilding care should also be taken to assess the substrate upon which the gilding was applied. Less common were techniques, which treated the gilded surface chemically. Theophilius, and Cellini both report some recipes on how “to colour the gold or gilding”.
In 2011 – 12 a group of restorers and conservationists at the Royal Institute for Cultural Heritage in Brussels worked to restore the Shrine of Our Lady of Huy from around 1260. In connection with this work, the group studied not only the ‘colouring’ of the shrine but also the ancient recipes. Recently an overview of this work was published in an article in the journal: Studies in Conservation
In the restoration-conservation practice of medieval art masterpieces, such as the Holy Lady Shrine from Huy, knowledge about the techniques used to create and shape them is of major importance, especially when they concern the surface finishing treatments. This influences the selection of methods employed for the conservation-restoration process. This paper discusses the method and the materials that might have been employed to modify the colour of gilding on silver. Recipes for chemically modifying the colour of the gilded surface can be found in medieval texts and might have been used on the masterpiece discussed in this paper. This article gives an overview of technical instructions related to this topic and presents a method to interpret their contents in order to be able to implement them. It reports observations carried out during the implementation tests, such as information about the temperature, timing, and other important elements. It concludes with the visual and the colorimetric results on the samples after application of the tested recipes.
The shrine is currently exhibited in the treasury of Collégiale Notre-Dame.
On Divers Arts
Ed. by John g. Hawthorne and Cyril Stanley Smith
Courier Corporation 1963 (2012)
Earliest (12th century) treatise on arts written by practicing artist. Pigments, glass blowing, stained glass, gold and silver work, more. 34 illustrations.