Thermoluminescence, or TL, has been used since the 1950s to determine the approximated firing date of pottery and burnt silicate materials.TL has a wide dating range; it has been used to date ceramics from a few hundred years old to geologic formations that are half a million years old.Raw clay will emit a strong thermoluminescent signal if heated without first being fired in a kiln.However, the act of firing drains away all the geological thermoluminescence acquired over millions of years, essentially setting the dating clock to zero.Tammy Rittenour and Kerry Riley organized a successful 2016 Rocky Mountain Friends of the Pleistocene field trip to southern Utah in mid-October.Please visit our 2016 RM FOP Field Trip page for details from the trip.The intensity of the light is proportional to the amount of energy, which in turn corresponds to the length of accumulation time.
Thermoluminescence (TL) is a faint violet-blue light that is emitted when a piece of fired pottery is heated at a sufficiently high temperature.
Once the pottery has cooled, the thermoluminescence begins to accumulate again at a constant rate.
When a sample from a piece being tested is heated in the laboratory the intensity of the light seen is directly proportional to the time that has elapsed since the piece was last fired.
Recently new techniques (optically stimulated luminescence dating) using lasers and sensitive detectors have been used to improve the light detection.
Samples require about 100 milligram and the sample collection and handling step is critical. The rate of energy accumulation depends on the amount of background radiation to which the object has been exposed.