Cobalt blue reproduction and characterisation of blue enamel recipes from The Handmaid to the Arts by Robert Dossie

摘要

The present work aims to give new insights into the study of blue enamels applied on stained glass. Selected blue enamel recipes from the treatise The Handmaid to the Arts (1758) by Robert Dossie were reproduced. Components such as lead can influence the final colour and appearance. Its use was important to the adhesion between the enamel layer and the glass surface. Colouring agents can also have an effect on the outcome. Powdered glass such as smalt can lead to a more predictable final colour, allowing the glass painter to foresee the result before firing the paint. The colour of the enamels was characterized by means of fibre optic reflectance spectroscopy (FORS), comparing the results with the ones obtained for four stained-glass panels from the Pena National Palace. The FORS technique was a good first approach for enamel characterisation, when is not possible to collect a sample for analysis.