To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.
This energy is lodged in the imperfect lattices of the mineral's crystals.
Powder samples (from pottery and bronze cores) are mixed with acetone and allowed to settle, so that fine grains, approximately 1/100mm. These grains are deposited and dried onto aluminium discs (for fine-grain analysis) or rhodium (for pre-dose analysis).
Any remaining powder is dried and used for radioactivity measurements to complete the dating calculation. When the glue is dry, they are cut into slices 1/4mm thick with a fine diamond blade. Each slice is soaked in acetone after cutting to remove the glue. The remaining core is crushed and used for radioactive analysis to complete the dating calculation.
The TL is measured using a sensitive detector called a photomultiplier tube.
Thermoluminescence (TL) dating of sediments depends upon the acquisition and long term stable storage of TL energy by crystalline minerals contained within a sedimentary unit.
The presence of rubidium and cosmic radiation generally play a lesser but contributory roll, and the total radiation dose delivered to the TL phosphor is modified by the presence of water.
As a result, there is no upper date limit set by the sensitivity of the method itself, although other factors may limit the method's feasibility.
Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.
Heating the mineral (or exposure to light) releases electrons, and produces a flash of light, setting the clock to 0 (maybe only partial).
Thereafter, luminescence accumulation is proportional to age.