Compositional investigation and phase identification of 13th century Anatolian Seljuk glazed tiles

Glazed tiles from five madrasas built in Anatolia by Seljuks during 13th century were examined using multi-analytical techniques to discover production processes, firing temperatures, raw materials and nature of colorants used. Turquoise colored glazes were assessed to be of the type tin-opacified lead-alkali whereas the violet-brown colored glaze was determined to be of the transparent alkali type. Copper and manganese were identified to be responsible for the turquoise and violet-brown color of the glazes, respectively. Firing temperatures of the glazes were estimated using polymerization indices calculated by using Raman spectra of the samples and assessed to be in the range of 800−1000 °C. Bodies of the glazes were determined to be produced using quartz, low calcareous and non-calcareous clays. No slip layers were observed between the glaze and the body in the samples. Gas bubbles observed inside the glaze layers in some of the samples suggested that glazes might have been applied on a non-fired body. Tin-opacified lead-alkali glazes investigated in this study were suggested to be produced in the specialist centers in Anatolia which were limited in quantity during the Seljuk period.