The influence of temper shape on the mechanical properties of archaeological ceramics

The influence of tempering on the mechanical performance of pottery is assessed. Emphasis is placed on the examination of the impact of temper shape (low vs. high sphericity) and extent of vitrification on the strength and toughness of the ceramic material. Measurements on experimental briquettes show that the replacement of platy phyllitic temper with bulky granitic temper results in a reduction in strength but, at least at very high firing temperatures, in an increase in toughness. The observed differences in strength reduction with different temper shapes is semi-quantitatively assessed by adapting the damaged zone model, developed previously to disk-shaped particles. The effect of temper shape on toughness is particularly pronounced at high firing temperatures, where platy temper results in significantly lower fracture toughness of the corresponding material.