A study of the mass-gain of ancient pottery in relation to archeological ages using thermal analysis

The study of mass-gain of ancient pottery in relation to archeological ages is of interest in the dating of pottery. Mass-gain takes place after firing by slow rehydration and rehydroxylation processes in fired-clay ceramics. In the present study, actual mass-gain values of pottery from distinct archeological periods (up to 6500 years BP) were obtained from the turn-over mass-loss values by using a thermal analysis method. Regression curves of the mass-loss percentages due to processes of dehydration, dehydroxylation and a combination of the two processes versus the median age (BP) of the pottery samples were obtained. The regression curves demonstrate that the actual mass-loss values of individual pottery samples generally increase over time. High correlation coefficient (R2) values are observed for regression curves of the average mass-loss values, which were calculated for the median age of all pottery samples of the same archeological period. The different factors that influence the mass-gain and lead to deviations in mass-loss values of individual pottery samples in relation to their ages are the type of fired clay, the amount of calcite, the amount of coarse particles (temper) in the pottery and the level of firing. In the present study the results were normalized without the amount of calcite in the ceramics. A precise dating of individual pottery samples according to other factors requires additional analysis methods, which will be applied in future work.