Thermogravimetric investigation of ancient ceramics

Sherds from restored ancient pots taken from archaeological sites of Siberian region (Late Bronze and Early Iron Age, IX-VIII to VII-VI BC) were investigated by thermogravimetry in order to define the effects of sampling. Three types of the sampling were (1) scanning through the inner surface of a pot, (2) outer surface, core, and inner surface of thick-walled sherds, and (3) random fragments of a restored pot. The results of the measurements were shown to depend on two factors, clay paste composition and firing conditions. Redistribution between mass loss at dehydration and dehydroxylation was detected for the ancient ceramics after 'mild' firing. The results of the measurements are explained in terms of a temperature profile throughout the wall of a pot during the thermal treatment under firing and cooking meal. The main conclusion of the work is that the thermogravimetric measurements will be very useful for the solution of archaeological problems only if the sampling is correct.