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Narrow rinds (under approximately two microns) are usually examined under a higher magnification. Hydration rinds smaller than one micron often cannot be resolved by optical microscopy. The Failure of Obsidian Hydration Dating: Sources, Implications, and New Directions. It is important to note that these values reflect only the reading uncertainty of the rim values and do not take into account the resolution limitations of the microscope or other sources of uncertainty that enter into the formation of hydration rims (Meighan 1981, 1983; Skinner 1995:5.13-5.19; Anovitz et al. Any attempts to convert rind measurements to absolute dates should be approached with great care and considerable skepticism, particularly when rates are borrowed from existing literature sources. When considered through long periods, the variables affecting the development of hydration rims are complex, and there is no assurance that artifacts recovered from similar provenances or locales have shared thermal and cultural histories. When a clearly defined hydration layer is identified, the section is centered in the field of view to minimize parallax effects. Four rim measurements are typically recorded for each artifact or examined surface. Obsidian-Hydration Dating: Its Past, Present, and Future Application in Mesoamerica. These cuts produce a cross-section of the artifact approximately one millimeter thick which is removed from the artifact and mounted on a petrographic microscope slide with Lakeside thermoplastic cement. A New Dating Method Using Obsidian: Part I, The Development of the Method.
In Current Directions in California Obsidian Studies, edited by Richard E. 48, University of California, Berkeley, California.
The most important of these are chemical composition and temperature, although water vapor pressure and soil alkalinity may also play a role in some contexts.
The effects of these variables have often been summarized and will not be discussed further here (Michels and Tsong 1980; Friedman and Obradovich 1981; Freter 1993; Hull 2001; Stevenson et al., 1993, 1998, 2000; Friedman et al. 1999, Ridings 1996; see Skinner and Tremaine 1993 for additional references).
In Advances in Obsidian Glass Studies, edited by R.
Empirical Determination of Obsidian Hydration Rates from Archaeological Evidence.