The clay core of bronze sculptures made by lost wax casting can also be tested.
Different materials vary considerably in their suitability for the technique, depending on several factors.
The heating must have taken the object above 500° C, which covers most ceramics, although very high-fired porcelain creates other difficulties.
It will often work well with stones that have been heated by fire.
In thermoluminescence dating, these long-term traps are used to determine the age of materials: When irradiated crystalline material is again heated or exposed to strong light, the trapped electrons are given sufficient energy to escape.
Thermoluminescence dating (TL) is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediments).Depending on the depth of the traps (the energy required to free an electron from them) the storage time of trapped electrons will vary as some traps are sufficiently deep to store charge for hundreds of thousands of years.Another important technique in testing samples from a historic or archaeological site is a process known as Thermoluminescence testing, which involves a principle that all objects absorb radiation from the environment.These imperfections lead to local humps and dips in the crystalline material's electric potential.Where there is a dip (a so-called "electron trap"), a free electron may be attracted and trapped.