it works by The thermoluminescence technique is the only physical means of determining the absolute age of pottery presently available. It is an absolute dating method, and do
…es not depend on comparison with similar objects (as does obsidian hydration dating, for example). 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). By comparing this light output with that produced by known doses of radiation, the amount of radiation absorbed by the material may be found. When pottery is fired, it loses all its previously acquired TL, and on cooling the TL begins again to build up. Thus, when one measures dose in pottery, it is the dose accumulated since it was fired, unless there was a subsequent reheating. If the radioactivity of the pottery itself, and its surroundings, is measured, the dose rate, or annual increment of dose, may be computed. 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. In all, close to two dozen physical quantities must be accurately measured to establish the relationship between doses of different kinds of radiation and light output, and to compute dose rate. A leaflet from Daybreak describing the TL technique in more detail and giving a bibliography will be provided to interested persons. The phenomenon of thermoluminescence was first described by the English chemist Robert Boyle in 1663. 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.S.. The Research Laboratory for Archaeology at Oxford, in particular, has played a major role in TL research. 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. Since the university laboratories involved with TL are research facilities, they generally will not accept art objects for authentication on a routine basis. The TL laboratory at Daybreak was established in 1977 to make TL available to the art community in general. ( Full Answer )