Dating services separated people
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.
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).
It is also rare that any information about the radiation from the burial soil can be obtained, as art objects are usually thoroughly cleaned.
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.
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.