Electrons from these substances get trapped in the mineral's crystalline structure, and continuing exposure of the rocks to these elements over time leads to predictable increases in the number of electrons caught in the matrices.But when the rock is exposed to high enough levels of heat or light, that exposure causes vibrations in the mineral lattices and the trapped electrons are freed.Luminescence dating (including thermoluminescence and optically stimulated luminescence) is a type of dating methodology that measures the amount of light emitted from energy stored in certain rock types and derived soils to obtain an absolute date for a specific event that occurred in the past.The method is a direct dating technique, meaning that the amount of energy emitted is a direct result of the event being measured.The phenomena of thermoluminescence (TL) or thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) are widely used for measurement of radiation doses from ionizing radiations, viz. The applications of TL are initiated in the field of Geology followed by Archaeology, personal dosimetry, material characterization and many more to name. Hubner, Untersuehungenzur Thermolumineszenz dosimetrie (TLD) mitdotierten Aluminiumoxid, Keramiken, Isotopenpraxis Isotopes in Environmental and Health Studies 12 (1976) 342. The TL technique has been found to be useful in dating specimens of geologically recent origin where all other conventional methods fail. TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.
Oxford Authentication Ltd authenticates ceramic antiquities using the scientific technique of thermoluminescence (TL).
Thermoluminescence was first clearly described in a paper presented to the Royal Society (of Britain) in 1663, by Robert Boyle, who described the effect in a diamond which had been warmed to body temperature.
The possibility of making use of TL stored in a mineral or pottery sample was first proposed by chemist Farrington Daniels in the 1950s. Applications and limitations of thermoluminescence to date quaternary sediments.
Materials of geological origin will have absorbed considerable quantities of radiation since their formation, so any human-caused exposure to heat or light will reset the luminescence clock considerably more recently than that since only the energy stored since the event will be recorded.
The way you measure energy stored in an object that you expect has been exposed to heat or light in the past is to stimulate that object again and measure the amount of energy released.