Phase and Composition Study of 18th Century Qallaline Tiles, Tunis

The potters of Qallaline (or Kallaline, from qallāl, meaning “potters” in Arabic), a district of Tunis (Tunisia) near the now-vanished Bab Kartâjanna gate, produced tiles from the 16th century until the end of the 19th century, with peak activity in the 18th century. These tiles, made from local clay, feature decorations influenced by Hafsid art, the Castilian Renaissance, the Spanish Baroque of the Valencia region, and Ottoman styles. Their characteristic color palette combines green, blue, and ochre. Representative sherds from various 18th-century sites were analyzed using SEM-EDS, portable XRF (pXRF), and Raman microspectroscopy. The results were compared with tiles from earlier (16th-century Iznik, Türkiye), contemporary (18th-century Tekfur Palace, Istanbul, Türkiye), and later (19th-century Naples, Italy) productions used for similar purposes. The chemical signature of the different cobalt ores used appears to depend primarily on the production period. The pastes used in Iznik, Tekfur, and Qallaline ceramics exhibit different compositions. Qallaline potters employed three types of pastes, varying in calcium content, which were used either separately or together within the same tile. In some cases, tin was also present in association with lead. The cobalts used at Qallaline originate from different sources than those used contemporaneously in Meissen (Saxony), as well as from those used in the decoration of Iznik tiles one or two centuries earlier, which are themselves comparable to the cobalt used in Persian mīnā’ī. The As, Ni, and Mn contents are similar to those of the cobalt employed at the Royal Manufacture of Sèvres, believed to have come from the Giftain Valley in Catalonia.