The case of Black and green tin glazed pottery from Barcelona between 13th and 14th century: analysing its production and its decorations

Black and green tin-glazed pottery is known to be one of the true majolica manufactures at Barcelona during the end of the medieval period. This pottery means the evolution of a production process for achieving opacified decorated tableware, started one century before, with the elaboration of what is known as archaic majolica. Black and green implies a new high variety of decorative motifs made in black, or in black and green, on a white opacified glaze prepared following a recipe adapted by potters to prepare the base glaze and to applicate the pigments for attaining the decorative patterns, characteristics of this period. Originally thought as imported from Valencia workshops, the development of different archaeometric projects conducted in the core of the ARQUB team, allows verifying an origin in Barcelona. Besides, recent excavations dated back to the 14th century provided a great number of Black and green sherds with new decorative motifs unknown up to now, allowing the specialists to create a new corpus of decorative patterns, which is still in progress. Based on insights obtained from those first archaeometric studies and considering the advances on the classification of decorations based on archaeological arguments, a new sample of Black and green sherds was selected for this study. The aim was to observe whether decoration and technique of manufacture could in some way be related, understanding the technical process as the selection and application of raw materials and the firing temperature at which this pottery was made. To achieve these objectives, X-ray fluorescence (XRF), X-ray diffraction (XRD), and Scanning Electronic Microscopy (SEM-EDX) have been performed. The results allow verifying the groups previously defined and to identify a new chemical group, probably related to a recipe for the body-paste different from the others. On the other hand, the study enabled us to observe differences also in know-how in firing, which in some cases seem to be connected with differences in the decorative motives, suggesting, perhaps, the discrimination of artisans