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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.Some clays are hardly thermoluminescent at all; some may not have a straight-line relationship between dose and TL; spurious luminescence due to chemical or pressure effects may mask the radiation-induced TL; occasionally, a condition called "anomalous fading", where part of the TL is unstable, may lessen the accuracy of the dose measurement.Generally speaking, when a sample is drilled and there is no information available about the burial environment, one may expect up to 40 per cent uncertainty.This is adequate for the purposes of authentication where the question is whether the piece was fired in antiquity or recently; it will not differentiate, say, between a classic Greek terra cotta and a Roman copy.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.While not so accurate as radiocarbon dating, which cannot date pottery (except from soot deposits on cooking pots), TL has found considerable usefulness in the authenticity of ceramic art objects where high precision is not necessary.
Finally, one has to make the measurements regardless of whether the TL of the clay is well-behaved or not. 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. When pottery is fired, it loses all its previously acquired TL, and on cooling the TL begins again to build up.It was employed in the 1950's as a method for radiation dose measurement, and soon was proposed for archaeological dating.By the mid-1960's, its validity as an absolute dating technique was established by workers at Oxford and Birmingham in England, Riso in Denmark, and at the University of Pennsylvania in the U. The Research Laboratory for Archaeology at Oxford, in particular, has played a major role in TL research.