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Using the end product of diffusion, a phenomenological model has been developed, based on certain initial and boundary conditions and appropriate physicochemical mechanisms, that express the HO concentration versus depth profile as a diffusion/time equation.
This technique used numerical calculation to model the formation of the entire diffusion profile as a function of time and fitted the derived curve to the hydrogen profile.Once an archeologist can control for the geochemical signature of the obsidian (e.g., the "source") and temperature (usually approximated using an "effective hydration temperature" or EHT coefficient), he or she may be able to date the artifact using the obsidian hydration technique.Water vapor pressure may also affect the rate of obsidian hydration.Over time, water slowly diffuses into the artifact forming a narrow "band," "rim," or "rind" that can be seen and measured with many different techniques such as a high-power microscope with 40-80 power magnification, depth profiling with SIMS (secondary ion mass spectrometry), and IR-PAS (infra red photoacoustic spectroscopy).In order to use obsidian hydration for absolute dating, the conditions that the sample has been exposed to and its origin must be understood or compared to samples of a known age (e.g.The FD equations are based on a number of assumptions about the behavior of water as it diffused into the glass and characteristic points of the SIMS H diffusion profile.
In Rhodes, Greece, under the direction and invention of Ioannis Liritzis, the dating approach is based on modeling the S-like hydrogen profile by SIMS, following Fick's diffusion law, and an understanding of the surface saturation layer (see Figure).
as a result of radiocarbon dating of associated materials).
Their initial work focused on obsidians from archaeological sites in western North America.
Several factors complicate simple correlation of obsidian hydration band thickness with absolute age.
Temperature is known to speed up the hydration process.
The reliability of the method based on Friedman’s empirical age equation (x²=kt, where x is the thickness of the hydration rim, k is the diffusion coefficient, and t is the time) is questioned from several grounds regarding temperature dependence, square root of time and determination of diffusion rate per sample and per site, apart of some successful attempts on the procedure and applications.