Glaze production at an early Islamic workshop in al-Andalus

The study and analysis of the materials found in one of the earliest Islamic glazed ceramics workshop in al-Andalus (Pechina) dating from the second half of the 9th century, including fritting vessels, kiln furniture, wasters and slags, and a glass chunk, have revealed the materials used and methods of production. Galena was oxidised to obtain PbO in the workshop. Fritting of the glaze involved a two-stage process for which two different types of vessels were used. The fritting process ended with a melt which was poured to obtain a high-lead glass. The ground glass was applied over the biscuit-fired ceramics, and fired to a temperature high enough to soften the glaze and adhere it onto the ceramic surface. Evidence of a similar process was found in a later workshop in San Nicolas (10th century) which demonstrates the persistence of the technique in al-Andalus during the caliphal period. There is little evidence of early Islamic glaze manufacture at kiln sites, and in contrast to the glass workshops, the glazed ceramics workshops have not been studied. Consequently, this study adds valuable information to the currently very limited knowledge about the early glaze technology in Dar al-Islam.