Multi-analytical study of the pigments in 17th Century Portuguese Azulejos

Abstract

Historic glazed tiles (azulejos) are an important part of the cultural heritage of Portugal. 17th century Portuguese azulejos were manufactured by the majolica process, in which the colours were applied over a white tin-glaze. The distribution of colours in the glaze depends on the pigment used. Lead-yellow and all colours obtained from it, such as lemon yellow, fern-green and orange remain mainly at the surface of the glaze, whereas cobalt blue and copper green sink and often disperse in the glaze. The layering behaviour in the glaze ensures that in cases of superposition the colours do not mix. We analysed the morphology and chemical composition of such colours using SEM/EDS analysis complemented by Raman spectroscopy and optical microscopy.