Director: Glenn Russell
E-mail: lithics@ucla.edu
Phone: 310.206.2171
Room: A 351 Fowler

Recent Advances in Obsidian Hydration Dating

The UCLA Obsidian Hydration Laboratory, one of the first laboratories of this type ever established, has over three decades of experience and work in the field of obsidian hydration dating. Recently, the lab has implemented the new "intrinsic water" method of obsidian hydration dating. This method is a departure from the old empirical approach in which hydration rates were constructed for each obsidian source separately.

The new method is based on an understanding of the significant variables that affect the hydration diffusion process. These include thickness of the hydration rind, the intrinsic water content of the obsidian artifact, and the effective hydration temperature (EHT) and relative humidity(RH) of the archaeological context from which the artifact was recovered.

The hydration rind is measured using a geological thin section type microscope. The intrinsic water content of each artifact is measured using a very precise density approach. The variables of EHT and RH are measured using salt cells which are buried in the archaeological site for a year. In the absence of salt cell data, EHT and RH may be estimated using local weather station data.

The result is an artifact specific hydration rate that can be used to calculate relative and absolute obsidian hydration rates. Because hydration rates are calculated for each artifact, it is no longer necessary to conduct XRF or other source identification procedures as part of the hydration dating process.

Laboratory services are available on a contract basis. In addition, we are interested in collaborating with archaeologists who are interested in the new method and who wish to test it on their own objects. We encourage requests for additional information on the new methodology. The laboratory also makes EHT and RH salt cells available to clients.