The thermoluminescence technique is the only physical means of determining the absolute age of pottery presently available.
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Heating these crystals (such as when a pottery vessel is fired or when rocks are heated) empties the stored energy, after which time the mineral begins absorbing energy again.
TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.
This energy is stored in the form of trapped electrons and quartz sand is the most commonly used mineral employed in the dating process.
Prior to the final depositional episode it is necessary that any previously acquired TL is removed by exposure to sunlight.
When a small sample of ancient pottery is heated it glows with a faint blue light, known as thermoluminescence or TL.
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.
Should I be concerned about artificial irradiation? If the radioactivity of the pottery itself, and its surroundings, is measured, the dose rate, or annual increment of dose, may be computed.
Warning about fakes using ancient materials What about airport x-rays and radiography? Thus, when one measures dose in pottery, it is the dose accumulated since it was fired, unless there was a subsequent reheating.