Using FT-IR spectroscopy for study of calcareous ancient ceramics

FT-IR spectroscopy was used for study of domestic Iron Age storage jars excavated at Tel Hadar on the eastern shore of the Sea of Galilee. The IR spectra are indicative of calcareous ceramic, showing Si-O and CO₃ vibrations characteristic of meta-clay and recarbonated calcite, respectively. Bands indicative of Ca-silicates were not observed in the spectra. The potters used calcareous raw material for the preparation of storage jars in order to reach low temperature firing. The firing at about 700-800 °C, was sufficient for decomposition of the calcite in the calcareous material. The large amount of calcite in the ceramic (39-57%) indicates that the consolidation of the storage jars also took place by recrystallization of microcrystalline calcite during the recarbonation process. Consolidation by cementation with calcite required lower firing temperatures than that necessary to complete the sintering of the clay.