Strength, Toughness and Thermal Shock Resistance of Ancient Ceramics, and Their Influence On Technological Choice

Abstract

The basic underlying theory for the strength, toughness and thermal shock resistance of brittle multiphase clay ceramics, together with the measurement procedures to determine these parameters, are ®rst outlined. Published experimental data obtained for test bars containing different types of temper and ®red to a range of temperatures are then compared both with theoretical predictions and between themselves. The results con®rm that to produce pottery with high strength requires high ®ring temperatures and low temper concentrations. Conversely, to produce pottery with high toughness and thermal shock resistance requires low ®ring temperatures and high temper concentrations, with platy or ®brous temper being most effective. There is no convincing published evidence that strength and toughness requirements were a signi®cant factor in determining the technological choices (clay type, temper type and concentration, and ®ring temperature) in the production of pottery used as containers for transport and storage. In contrast, the routine use of high temper concentrations and low ®ring temperatures in the production of cooking pots suggests that the requirement for high thermal shock resistance was a factor that at least in¯uenced technological choice in this case. In addition, there is some evidence that limestone and shell were, on occasions, deliberately chosen as temper in cooking pots. The need to take into account the crucial role that the full range of environmental, technological, economic, social, political and ideological factors have in in¯uencing technological choice is also emphasized. This review highlights the fact that our current understanding of the factors determining strength, toughness and thermal shock resistance of clay ceramics is still far from complete. Further systematic measurements of these parameters, together with the establishment of a systematic database of the range of technological choices associated with the production of cooking pots, are therefore to be encouraged.

Defining pottery use and animal management at the Neolithic site of Bylany (Czech Republic)

“…Mean porosity of the studied potsherds was 23% and they contained a predominance of 469 micro-and mesopores, which would aid the protection of adsorbed lipids during burial. The 470 porosity measurements also indicated that pottery production technology at Bylany was well-471 developed, which would have influenced the ways vessels were used and the extent to which 472 they survived in the archaeological record (Tite et al, 2001). The slightly acid pH burial 473 conditions at the site appear favourable for lipid preservation (e.g.…”

Late Roman cooking pottery from the Tavoliere area (Southern Italy): raw materials and technological aspects

“…Medium synterization grade and non-calcareous coarse temper represented good technological choices to enhance the thermal shock resistance of the pots and to avoid lime spalling [31,32].…”

Pottery kiln and drying oven from Aventicum (2nd century AD, Ct. Vaud, Switzerland): Raw materials and temperature distribution

“…This vegetal temper was burnt out during many firing cycles and left elongated relict voids. Such secondary porosity generated during the firing/use of the bricks in the kilns, as well as that induced by coarse NPIs from the use of non elutriated clay, enhanced the thermal insulation of the kiln (Hein and Kilikoglou, 2007;Hein et al, 2008;Tite et al, 2001). Since very few samples of brick show very high sintering (i.e.…”