Ancient techniques (invited)

Abstract

Ancient ceramics may be characterised by their magnetic hysteresis loops. Spontaneous and remanent magnetization and coercivity can be used to distinguish groups of ceramics fired in different conditions. Information about the firing conditions is obtained by comparing the magnetic parameters of the sherds with those of laboratory-fired paeleosols. The method is illustrated with reference to contemporary red, buff and grey ware (c 3000 BC) from the period II of Tureng Tepe and Tepe Hissar, two related sites in northeastern Iran. In some cases the firing temperature can be estimated to within 50 C, and groups of sherds fired in oxidizing, reducing or mixed atmospheres are identified. An explanation of the firing temperature dependence of the hysteresis loop parameters in the range 400–1200 C is based on the proportions of iron diluted in silicates and in superparamagnetic or stable iron oxide particles, derived from magnetic and Mössbauer data. An assessment is given of the potential of simple magnetic measurements in archaeometry.