Thermoluminescent Natural radioactivity causes the number of trapped electrons to build up.The older an object, the more trapped electrons it will have.When collecting samples for thermoluminescence dating, several samples from different vessels should be taken, not smaller than 1 gram.Samples should not be exposed to heat and powdery examples should not be exposed to bright light.
This last procedure involves the use of a radioactive source, though very weak.
When the object is heated to 350 degrees Celsius the trapped electrons are released and this is called a clock resetting event.
From this time on, electrons start to build up again because of the natural radioactivity.
This usually occurs when the items are heated to 350 degrees Celsius.
Therefore, in archaeology, thermoluminescence dating works best for ceramics, cooking hearths, incidentally fire-cracked rocks, and deliberately fire-treated rocks, such as flint or chert.