White on blue: A study on underglaze-decorated ceramic tiles from 15th-16th-century Valencian and Sevillian productions

This study characterises and compares tin-opacified underglaze-decorated tiles from Valencian and Sevillian provenances. This technique, where the cobalt and manganese pigments are applied below an opaque white glaze, was used in the Iberian Peninsula between the 14th and early 16th centuries. The chemical and morphological characterisation of the glazes was performed by Optical Microscopy (OM), Scanning Electron Microscopy with Energy-Dispersive X-Ray Spectroscopy (SEM-EDS), μ-Raman Spectroscopy, and μ-Particle-Induced X-Ray Emission (μ-PIXE). Both the morphology of the glazes and their chemical composition allowed for the distinction between the two production centres. Sevillian glazes exhibit a thicker pigment layer, as well as higher SnO2 and lower K2O contents than the Valencian ones. Furthermore, the SEM analysis of cobalt pigment particles identified an interior nucleus rich in Co, Fe and Ni, and an exterior layer rich in Si, Ca, Mg and Na,suggesting that the pigment was used mixed with clay or sand

The Glaze Technology of Hispano-Moresque Ceramic Tiles: A Comparison Between Portuguese and Spanish Collections

For the first time, Hispano-Moresque glazed tiles from Portuguese and Spanish collections were studied together and compared. This work is included in a wider study tackling the technology of Hispano-Moresque tile production from several collections in the Iberian Peninsula. While showing many similarities, differences were identified between collections, regarding both chemical and morphological characteristics. The collection from the Mosteiro de Santa Clara-a-Velha (Coimbra) stands out from the other collections, with higher SnO2 content (up to 14¿wt%), the highest Fe2O3 contents in amber glazes and a Ca-rich interface layer (mostly comprised of wollastonite, CaSiO3). Samples from Palácio Nacional de Sintra (near Lisbon) and Seville-attributed samples (from the Instituto Valencia de Don Juan) are chemically similar, except that most Sintra's samples display a K-rich glaze/ceramic interface, whereas the ones from Seville exhibit both K-rich and Ca-rich inclusions. The samples attributed to Toledo show glazes with many inclusions, contrasting with the homogeneous glazes in most Hispano-Moresque tiles. From these results, we identify differences that can be used as markers in future studies on Hispano-Moresque tiles.Peer Reviewe