New insights in technology characterization of medieval Valencia glazes

Romero-Pastor, J, García-Porras, A, Van Grieken, R, Potgieter-Vermaak, S, Coll-Conesa, J and Cardell, C (2015) New insights in technology characterization of medieval Valencia glazes. X-Ray Spectrometry, 44. ISSN 0049-8246

Preview

Available under License In Copyright. Download (2MB) | Preview

Abstract

This study shows the first Raman Microscopy (RM) and SEM-EDX characterization of two 14th and 15th century lead-glazes and lustre ceramics from the Manises and Paterna workshops (Valencia, Spain) produced after the Aragon Christian conquest of the Iberian Peninsula (14th century). According to experts, these coetaneous ceramics were most probably involved in a process of technological transfer from the Islamic area of Southeast Spain to the Christian area of Valencia (East Spain) at the beginning of the 14th century; later on the celebrated Manises and Paterna workshops were formed. Although these ceramics have been studied widely in terms of production technology (ceramic body, glazes and lustre) using an array of diverse analytical techniques, until now a RM study has not been carried out. This paper presents results regarding the complex chemical composition of the glaze and lustre coloring agents and the quality of color manufacturing processes, elucidating firing conditions via spectral components analysis (i.e. Qn for stretching/bending components) and polymerization index (Ip), emphasizing chronology and pigment technology changes between both Valencian workshops. Coloring agents identified in glazes and lustres were cobalt present in blue glazes, copper in greenish glazes, copper and cobalt in the turquoise glaze and pyrolusite in black glazes. Tin oxyde was used as an opacifier in white glazes. Two lustre manufacture recipes were recognized mainly based on copper and silver compounds. Calculated firing temperatures were up to 1000ºC for white glazes and up to 600ºC for lustre and color glazes.