Carbon dating artwork
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.
Unfortunately, it is not possible to achieve this precision for the majority of art objects.
Among the reasons for this is the small amount of material that may be taken for testing.
These will give an authentic date for a bogus object.
It must be realized that TL dating is but one of the criteria for judging authenticity.
This radiation may in some cases contribute over half the total dose.
The phenomenon of thermoluminescence was first described by the English chemist Robert Boyle in 1663.
Some of these are quite easy to detect; some quite difficult.
For example figures, normally modeled, may be carved out of brick or assembled out of fragments.
Using this information often reduces the uncertainty to 15-25 per cent. Nearly any mineral material which has been heated above 500C at a time one wishes to know is a candidate for TL dating. Porcelains, being nearly vitrified, are a special case requiring a fairly large solid core sample, and TL dating of intact objects is not recommended because of the damage caused by sampling.
Most porcelain dating is done for insurance purposes on broken objects.