The production technology of Portuguese 16th-17th-century faience and its comparison with coeval azulejos
COENTRO S. 1,2, BANDIERA M. 1, VERONESI U. 1, LANCRENON V. 1,3, PAIS A. 4, MIMOSO J. 5
1 VICARTE - Research Unit "Glass and Ceramics for the Arts", NOVA School of Science and Technology, Caparica, Portugal; 2 Department of Conservation and Restoration, NOVA School of Science and Technology, Caparica, Portugal; 3 Chimie ParisTech – PSL, Paris, France; 4 Museu Nacional do Azulejo, Lisbon, Portugal; 5 Laboratório Nacional de Engenharia Civil, Lisbon, Portugal
Portuguese faience (or maiolica) technology is believed to date back to the early 16th century. The arrival of Flemish maiolica potters in Lisbon is appointed as a decisive aspect of introducing and developing this “new” ceramic technology, and their role is documented both in written documents and in the first Portuguese tile panels (azulejos). Apart from azulejos, however, there are no other known 16th-century Portuguese faience productions with secure dates and authorship, although we know they were both produced in the same workshops.
In this study, we characterised a set of archaeological faience fragments from the Monastery of Santa Clara-a-Velha, in Coimbra, believed to be dated from the 17th century or the late 16th century. The studied set is representative of the different faience qualities used in the Monastery, including porcelain imitations.
The analytical methodology included SEM-EDS (Scanning Electron Microscopy with X-Ray microanalysis), µ-EDXRF (Micro-Energy-Dispersive X-ray Fluorescence), µ-Raman spectroscopy, optical microscopy and colourimetry.
Preliminary results have shown that all objects were made with calcitic clays and that the CaO contents alone allow the distinction of two groups using different clay mixtures. The chemical composition and morphology of the glazes also show different characteristics in thickness, homogeneity and PbO/SiO2 ratios. Considering these results in the context of the better-known evolution of azulejo technology, part of the faience objects may be dated to the 16th century, whereas the majority is consistent with the chemical composition and morphological features of 17th-century production.
The coloured decoration was obtained with cobalt blue used alone or with manganese brown over the white glaze. Among the different blue shades analysed by colourimetry, one stands out for its darker “purple-like” tone, which was identified as a mixture of cobalt and manganese.
This study connects two research projects funded by the Portuguese Foundation for Science and Technology. These projects aim at unveiling the connection between azulejo and other faience productions by researching their glaze technology and coloured decoration throughout the centuries.