This technique is specific for any material containing various minerals, mainly quartz or feldspar, which has undergone prolonged heating at temperatures of the order of a few hundred degrees.
They can be dated:ceramics, terracotta and bricks, porcelain, furnaces, hearths, fusion lands. For them you can get of standard (and in correct sampling conditions) dating in the indicative age range between 50 and 600,000 years.
A non-negligible fraction of the usual constituents of ceramic (quartz and feldspar, for example) are thermoluminescent:that is, these materials store in stable traps the electrons that have undergone an interaction with alpha, beta and gamma radiation due to natural radiation.
The release of electrons from the traps occurs as a result of the transfer of thermal energy by heating to temperatures of the order of several hundred degrees centigrade, and is characterized by a light emission:thermoluminescence.
The firing of the ceramic in the kiln eliminates any TL accumulated during the geological existence of the clay and of any constituents added to the mixture:from this moment, the TL begins to increase again over time, the more rapidly the greater the concentrations of radioactivity in the ceramic and in the environment.
The quantity of TL observed is therefore an indicator both of the age of the object and of the irradiation which was subjected.
Measured the TL of a sample, and therefore, indirectly, the amount of radiation that passed through it, and measured its radioactivity and that of the environment, we arrive at the fundamental equation of age , which in its simplified form is given:
ETA '(years) =Total radiation absorbed / Radiation absorbed annually
Dating with TL therefore refer to the last firing undergone by the object;
In the interpretation and evaluation of the results, this must always be kept in mind because it could lead to incorrect evaluations for materials that for example may have been subjected to fire, or accidentally heated or restored, or subject to the practice of reuse.
Like all physical measurements, the ages obtained with these techniques are always accompanied by inaccuracy, which means that the time interval within which cooking took place, centered on the age of maximum probability. Taking into account all the factors involved and the complexity of the necessary experimental evaluations, an average global error of 7-10% is estimated, which can only be reduced to 5-6% in particular cases.