Portuguese 16th century tiles from Santo Antonio da Charneca's kiln: a spectroscopic characterization of pigments, glazes and pastes

The first archaeological evidence reported for tile production in Portugal was discovered in Santo Antonio da Charneca (SAC), late 15th or early 16th centuries' pottery kiln, south riverside of Tagus River. Samples from this kiln were studied with the use of non-invasive spectroscopies, namely, -Raman, ground-state diffuse reflectance absorption, Fourier transform infrared and particle-induced X-ray or X-ray fluorescence emission. These results were compared with the ones obtained for coeval tiles produced in Seville, Spain, originated from Portuguese archaeological sites, because it is well know that the Portuguese King Manuel the First imported in 1498 significant quantities of those tiles to decorate several palaces. The obtained results provided new spectroscopic insights, used to establish similarities but also clear differences regarding the SAC and the coeval Seville tiles found in Portugal. White glaze from both tiles gave evidence about the use of tin oxide as whitening agent and lead oxide as glassy agent. Cobalt oxides were also used as blue pigments in the two production centres. The brown and amber pigments in the samples from SAC derive from the manganese oxides dispersed in the lead-tin glaze, and kentrolite crystals were identified by -Raman in these tiles. In the arista and cuerda-seca tiles from Seville, diopside was detected. Divalent copper also exists in the green glaze matrix but in small amounts, which did not allow the Raman detection of the copper compound's microcrystals. However, diffuse reflectance measurements point to malachite green as responsible of green coloration. The Seville pastes contain calcium carbonate, although the SAC pastes do not evidence significant amounts of that compound in its composition. All the SAC pastes evidenced a high silica level, and quartz and anatase were clearly detected in the paste and possibly kaolinite. The Raman signals of orthoclase and calcium carbonate were detected in the Seville tiles. Copyright (c) 2014 John Wiley & Sons, Ltd.