Authentication of terracotta based on thermoluminescence (TL), which gives an estimate of the age of the last heating of the material, with an uncertainty of about 20%. This requires the use of a drill 2mm in diameter and 5mm deep.
The TL is a physical phenomenon related to the ability of certain crystals to accumulate energy from environmental radioactivity and restore this energy as light when heated.
To date the heating of a clay, the sample is subjected to a high temperature (up to 500 ° C): the amount of light emitted is proportional to the time since the last firing.
Taking into account an average level of natural radiation, we can estimate the approached date of the last heating of the sample (test of thermoluminescence).
Dr Armel BOUVIER
operating our new TL machine LexsygSmart
For the recently heated object, the thermoluminescence curves have a very low intensity (light emitted is almost nul). The estimated length then gives a recent age.
For an antique, thermoluminescence curves (red) have a high intensity (light emission). In this case, the age of the last heating is 2000 ± 400 years.
Today, to detect elaborate fake objects, it is often necessary to complete the thermoluminescence approach with visualization of the internal structure of the object, using X-ray radiography or CT scan.
The combination of these two techniques (TL & Image), combined with stylistic analysis, guarantees the authenticity of an object in terracotta.