But OHD is troublesome in regions like the Andes mountains of South America, where people brought their obsidian artifacts across enormous ranges in altitudes, from the sea level coastal regions to the 4,000 meters (12,000 foot) high mountains and higher.
Even more difficult to account for is differential glass chemistry in obsidians.
The measurement of rind growth since the break can be done with a piece of equipment that probably already exists in most laboratories. The problem is, the constant (that sneaky D up there) has to combine at least three other factors that are known to affect the rate of rind growth: temperature, water vapor pressure and glass chemistry.
Temperature fluctuates daily, seasonally and over longer time scales in every region on the planet.
By targeting protected fissures not exposed to surface weathering effects, a consistent series of hydration readings has allowed age determinations of an obsidian mine site where the radiocarbon dates are unreliable, or fall within the undateable “modern” of the last 300 years.
The results of this approach, including long term laboratory-based hydration rate determinations, show that obsidian hydration dating is a viable dating system free of dependence on other dating methods to provide its time constants.
Despite its limitations, obsidian hydration dates are far less expensive than radiocarbon, and it is a standard dating practice in many regions of the world today.
This article is a part of the guide to the Scientific Dating Methods, and the Dictionary of Archaeology.
Archaeologists recognize this and started creating an Effective Hydration Temperature (EHT) model to track and account for the effects of temperature on hydration, as a function of annual mean temperature, annual temperature range and diurnal temperature range.
Sometimes scholars add in a depth correction factor to account for the temperature of buried artifacts, assuming the underground conditions are significantly different than surface ones--but the effects haven't been researched too much as of yet.
The effects of variation in water vapor pressure in the climate where an obsidian artifact has been found have not been studied as intensively as the effects of temperature.