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Abstract
A few decades ago, heritage scientists and art historians started to study the ancient surface colouring techniques of metal art pieces. Colouring of copper and silver has already been broadly studied but no works on gold have been reported yet. This knowledge can be very important for art and technology history, conservation–restoration and surface sciences. This paper contributes to the investigation of the oldest recipe known so far to colour fire gildings. The chosen model samples, the mixture and the application of the recipe have been summarised by referring to the ancient writings known as the Arab and Syrian Alchemist Collection of M. Berthelot. The main aim of this research is to study the colour change obtained by applying the above mentioned recipe, and to identify the processes involved during this colour change. Digital imaging and scanning electron microscopy in combination with colorimetric measurements and elemental analysis have been performed to characterise the colour change and to identify its origins.
For his help and tutorial on the use of the FESEM, we gratefully acknowledge Jon Ustarroz from the Research Group Electrochemical and Surface Engineering (SURF) from the VUB. The research project: ‘Colorando Auro’ Medieval goldsmith’s art and ancient recipes for colouring gold: an analytical approach (2009–2012), leading to these results received funding from the Belgian Science Policy (SPP).
Notes
*,†Temperatures were assessed with a thermocouple (Hanna Inst., −50 to 1350°C±0·2%) positioned directly against the back of the sample.
This paper is part of a special issue on Arts and Surfaces