Glazed Tiles from a Chateau of the Duke de Berry (Mehun-sur-Yèvre, End of the 14th Century): Research of Technical Indicators

At the end of 14th century, ceramists from Valencia (Spain) will export their know-how to France at the request of the duke Jean de Berry (1340 - 1416). New materials and advanced techniques arc thus put in an exchange context between two European areas (Gerona and Bourgogne). A characteristic of the produced glazed ceramics is to present a blue decoration, which is innovating at this time in France. In this study, we tried to complete the data collected by the archaeologists and to determine the physical characteristics of the materials (colouring agents, texture and components) and clues concerning the manufacturing techniques. The study reveals that the tiles arc covered with lead glazes or alkali-lead glazes, which are opacified with abnormally high tin rates (up to 36 % SnO2). For the monochromic tiles, the alkali-lead glazing mixtures were applied on calcareous supports, which were fired before a second firing (for the glaze). For the polychromic tiles, the glazes are alkali-lead containing on the tiles with a white support whereas they arc lead containing for the red supports. The difference in the colours of the calcareous bodies is due to the variation of the calcium and iron content and of the calcite concentration. The used colouring agents are traditional : iron, manganese, copper and cobalt respectively for the yellow, Parma, turquoise blue and blue colours. The yellow to brown decorations correspond to lustre ware decorations.