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.

This radiation may in some cases contribute over half the total dose.

Finally, one has to make the measurements regardless of whether the TL of the clay is well-behaved or not.

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.

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.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.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. 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.