The age of the pottery, in principle, may then be determined by the relation Age = Accumulated dose / Dose per year Although conceptually straightforward, TL has proven to to be far from simple in practice. Should I be concerned about artificial irradiation? If the radioactivity of the pottery itself, and its surroundings, is measured, the dose rate, or annual increment of dose, may be computed. By comparing this light output with that produced by known doses of radiation, the amount of radiation absorbed by the material may be found. Most mineral materials, including the constituents of pottery, have the property of thermoluminescence (TL), where part of the energy from radioactive decay in and around the mineral is stored (in the form of trapped electrons) and later released as light upon strong heating (as the electrons are detrapped and combine with lattice ions).Drilling, the usual method of sampling, introduces some uncertainty.It is also rare that any information about the radiation from the burial soil can be obtained, as art objects are usually thoroughly cleaned.
In some categories of objects, from China, for example, the actual age is quite precisely known for short-lived styles, and it is possible to work "backwards" to get information about the environment in many parts of the world, and some other parameters not usually measurable for art objects.WARNING ABOUT FAKES USING ANCIENT MATERIALS Recently there has been a spate of forgeries devised expressly to attempt circumventing TL dating.These use pottery of the appropriate period to construct objects.Much stoneware is not so hard as porcelain and may be sampled by drilling.The clay cores from lost wax metal castings may readily be tested. Warning about fakes using ancient materials What about airport x-rays and radiography? Thus, when one measures dose in pottery, it is the dose accumulated since it was fired, unless there was a subsequent reheating.