Rehydroxylation: a promising technique for ceramic dating

The kinetics of expansion in ceramic materials due to rehydration and rehydroxylation was investigated since the early XX century as a cause of crazing in glazed ceramics. Since then, the study of expansion and mass gain of ceramic has been studied extending the monitored times and modeling the involved processes. In the last 20 years, the interest in this process grew due to its possible application in the dating field, supporting well-established techniques such as thermoluminescence and optically stimulated luminescence. The principle of the dating technique is based on the fact that after the firing all water and hydroxyl molecules are desorbed from the ceramic structure, and after cooling are slowly adsorbed following a mathematical law. Nowadays, the correlation between time and mass gain is well established, but there is still no agreement on the mathematical model of the rehydroxylation process, and on a reliable protocol to date the materials. However, promising results have been reached, and more efforts must be put into the study of the role of involved parameters (storage temperature, activation energy, experimental setup...). Considerations on the last point will be shown, together with experimental evidence collected at Lambda (Laboratory of Milano Bicocca university for Dating and Archaeometry).