Thermoluminescence (TL) dating is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediments).
As a crystalline material is heated during measurements the process of thermoluminescence starts.
The amount of light produced is proportional to the number of trapped electrons that have been freed which is in turn proportional to the radiation dose accumulated.
In order to relate the signal (the thermoluminescence—light produced when the material is heated) to the radiation dose that caused it, it is necessary to calibrate the material with known doses of radiation since the density of traps is highly variable.
In the process of recombining with a lattice ion, they lose energy and emit photons (light quanta), detectable in the laboratory.
Thermoluminescence emits a weak light signal that is proportional to the radiation dose absorbed by the material. The technique has wide application, and is relatively cheap at some US0–700 per object; ideally a number of samples are tested. The destruction of a relatively significant amount of sample material is necessary, which can be a limitation in the case of artworks.