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 an absolute dating method, and does not depend on comparison with similar objects (as does obsidian hydration dating, for example).The longer the pottery is in the ground, the more radiation dose it will absorb, causing more electrons to be excited into trap states.
When dates of a number of sherds associated together are averaged, the error is reduced typically to 7-10 per cent. The succeeding 30 years, and increased understanding of the dosimetry, have not brought much improvement.Unfortunately, it is not possible to achieve this precision for the majority of art objects.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.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.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.
A set of criteria for acceptable dates is proposed.
When pottery gets covered in the ground, radiation from the earth starts to energize (excite) the electrons of these crystalline materials, putting them into “trap states.” This is a measure of the radiation dose.
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.
However, it’s well known among radiation physicists that RDRs vary with location, season, solar activity, and even time of day.