How-to · authentication
Ceramics: what a thermoluminescence test does and does not tell you
TL dates the last firing of a ceramic to within about 20 %; it cannot see restoration, and a small drilled sample is the price.
1. Understand what is measured. Thermoluminescence reads the light released when minerals in fired clay are re-heated; the signal has accumulated from natural radiation since the last firing, so its size is a clock for that firing.
2. Expect a range, not a date. Laboratories report a firing date with an uncertainty of typically ±15–25 % of the age: ancient versus modern is a confident call, a century either way is not.
3. Choose the sampling spot with the laboratory and photograph it. A few hundred milligrams are drilled from an inconspicuous place; the report should show where, because TL tests the sample, not the object — a genuine sherd built into a modern vessel passes where it was drilled.
4. Pair it with UV. Most fills, adhesives and overpaint fluoresce differently from fired clay, so a UV pass shows the restoration that TL cannot see; read the report's own estimate of restoration alongside it.
5. Record the laboratory, report number and date under Authentication with the method set to thermoluminescence, attach the report to the Vault, and let the certificate print the opinion with its method. Oxford Authentication and Ralf Kotalla are the laboratories the trade names most.
Sources
Cite this article
Stratum Study. "Ceramics: what a thermoluminescence test does and does not tell you" (How-to). Stratum Study pack 2026.09, as of 2026-09-20. https://stratum.black/study/how-to/how-to-ceramics-thermoluminescence. Accessed 2026-09-21.
@misc{stratum-how-to-ceramics-thermoluminescence,
title = {Ceramics: what a thermoluminescence test does and does not tell you},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/how-to/how-to-ceramics-thermoluminescence}},
year = {2026},
note = {How-to article, Stratum Study pack 2026.09, as of 2026-09-20; sources: stratum. Accessed 2026-09-21.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.