Micromorphology Used in Search of Understanding Production Technologies of Historical Turkish Ceramics.
Ahmet Ruhi Mermut, Univeristy of Saskatchewan, 238 Willoghby Cres., Saskatoon, SK S7N 5A8, Canada
Earlier studies carried out on the historical Turkish ceramics show that they were produced with great skill and high standard technical knowledge. The main ingredient of the wares was white clay filtered through specially woven cloth to remove impurities. The other additives were ground flint, frit (recycled highly vitrified glass fragments) and clay in the proportions of 10:1:1. Each of the Turkish ceramics of different periods was stated to be a culture on their own due to their ingredients or firing technologies. However the well established technology, with the buried furnaces, of the 16th Century Iznik pottery was much superior to earlier productions (12th Century), because of firing temperatures that may be attributed to the potters of KŁtahya and Iznik. The Iznik ceramics of the Seljuk and Ottoman Periods, we studied, have been unique in the sense of their resistance to degrading forces of nature as well as their incomparable over slip/glaze decorations with utmost matching properties to the underlying slip and body. The long-lasting decorations in the glaze were most probably bound to the ideal mixtures of raw material, which were composed of the quartz-rich skeleton (the coarse fraction) with dominantly kaolinitic and illitic clays (the fine fraction) - determined by x-ray diffraction- of the body developing to uniform microstructural patterns and intergrading to an interlayer (between the slip and the body) with the preferred orientation of elongated/oval pores, together with vitrified clay platelets coalescing in the matrix, determined by scanning electron microscope (SEM). The high temperature minerals of pseudowollastonite and forsterite were also observed in rounded pores in the glaze and in irregular pores of the interlayer and the body as anastomosing or radial clusters. Repeated clay/stress coatings/domains were observed around spheroidal secondary iron-rich mineral nodules, determined by the SEM and EDAX, as well as around irregular or rounded pores due to the stress created by the gas pressure against the clayey matrix during the solid to gas transition phase as the temperature rises. Ultimately, the buried furnaces of the period with uniform rates of heating and cooling are responsible for the development of the phenomena mentioned above as well as in our earlier studies related to furnace designs. The highly vitrified surfaces within the matrix may be attributed to the high potassium and silica contents, inherited from the raw material mixtures. Simulation studies are underway to translate the unique past indigenous technologies into the contemporary ceramic industry.