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.
The longer the pottery is in the ground, the more radiation dose it will absorb, causing more electrons to be excited into trap states.
Natural crystalline materials contain imperfections: impurity ions, stress dislocations, and other phenomena that disturb the regularity of the electric field that holds the atoms in the crystalline lattice together.
This leads to local humps and dips in its electric potential.
Both assumptions become less realistic with the passage of time.
Another problem with the TMRD is the calibration of the detector, since different crystals in an artifact can contain different amounts and/or types of luminescence material.
For instance, it is possible to date the wood support of a panel as well as canvas.
The three most important dating techniques which are useful for the analysis of works of art are: Thermoluminescence (TL), Dendrochronology (DC), and Carbon 14 (C15). It dates items between the years 300-10,000 BP (before present).
When scientists pull pottery from the ground, they use heat or lasers to de-excite these electrons out of their trap states back to their original state. Scientists measure the amount of light to get the total measured radiation dose (TMRD).
They divide this by an assumed radiation dose rate (RDR) to estimate the pottery’s age.
Where there is a dip (a so called 'electron trap'), a free electron may be attracted and trapped.