Microstructural and compositional studies of the technology and durability of ceramic glazes from Nippur, Iraq, ca. 250 B.C.-1450 A.

A collection of glazed sherds from the 1989/1990 excavation seasons at Nippur, Iraq, was studied in order to characterize the glazing technology at this site in the Seleucid through Ilkhanid periods (ca. 250 B.C. to ca. 1450 A.D.). The use of a high-magnesium alkali-lime-silicate composition is shown in all periods studied. A high degree of variability was found in early Islamic glazes, suggesting multiple locales of production, probable either sites or workshops. The increase in experimentation with glaze compositions, opacifying agents, color and visual effects indicates considerable experimentation within the framework of an established technology that we hypothesize was continuous in this region, although we lack the archaeological proof. In addition to the studies of technology, the effect of heterogeneities on degradation of the Nippur glazes was examined. Dynamic imaging microellipsometry used on replicate glasses in in-situ measurements showed increased durability near inclusions. Residual stress fields surrounding the heterogeneities influenced the results and decoupling of chemical and mechanical factors was not possible.