Protocols for laboratory hydration of obsidian, and their effect on hydration rate accuracy: A Monte Carlo simulation study

Laboratory hydration of obsidian is based on the principle that the measurement of water penetration at high temperatures allows computation of hydration rates at archaeological temperatures. Accuracy of the laboratory hydration method is sensitive to the details of the laboratory and analysis protocols employed. We present the results of a simulation study showing that accuracy of the standard protocol is poor, but is improved by longer hot-soak times, more accurate hydration rim measurements, and use of statistical weighting factors in the analysis. A revised protocol is proposed which permits hydration rate development with accuracies of 10-15%. However, inherent limitations of optical microscopy make further improvements difficult and the measurement of hydration layers using alternate technologies is recommended.