Abstract Limestone temper is common in Late Woodland period pottery from the central United States. Calcium carbonate in the mineral form of calcite, the predominant component of limestone, makes sticky clay more workable, but it also causes pots to spall if fired over 600°C. the low end of the open-firing temperature range. A test of performance characteristics of limestone-tempered prehistoric pottery replicates demonstrates that they are significantly more resistant to mechanical stress than are grit-or grog-tempered replicates fired to 600°C. Limestone-tempered pottery, also appears to be more resistant to thermal shock because the calcium carbonate allows for thinner vessels to be made and possibly because the expansion rate of calcite is very similar to that of clay. Some effort must have been taken by prehistoric potters to overcome the spalling produced by limestone temper, suggesting that the inclusion of limestone was a technological shift requiring refinement of pottery-manufacturing techniques.