Thermoluminesence (TL) and Optically Stimulated Luminesence (OSL) are related techniques which measure when objects were last heated (TL) or when buried deposits were last exposed to light (OSL).TL and OSL are known as 'electron trap' techniques.Even so, for the past 5000 years they are less accurate than other dating methods like radiocarbon.Part of this is the ordinary glow of burning, the remainder is due to escape of these trapped electrons and this is measured.These techniques can date objects up to 50,000 years old, although both are more accurate within the past 10,000 years.The object will then begin to trap electrons again.These electrons can be released and counted in a laboratory to give a date since the object was fired (TL).
Some soils can have their electron 'clocks' reset simply by being exposed to sunlight.
If they are then buried beneath later deposits, they begin to trap electrons again and can be dated by similar methods (OSL).
Some natural materials such as various stones and soils (and also things made from them, such as pottery and stone tools) absorb or 'trap' naturally occurring electrons from their surroundings.
This happens at a known and regular rate until the material becomes saturated with electrons after about 50,000 years.
This produces a date for the burial of the deposit.
The object to be dated is heated in a laboratory until it glows.