Thermoluminescence (TL) dating
Scientific method dating ceramics by measuring trapped electron-energy released as light when the clay is reheated. Reliable; the documented forgery vector is recomposition of ancient shards onto modern bodies, not the TL technique itself.
Thermoluminescence (TL) dating measures the accumulation of trapped-electron radiation energy in the crystalline mineral inclusions of a fired ceramic clay body. The clay-body radiation accumulates from the moment of original firing onwards; reheating in the laboratory releases the energy as measurable light. The light output, calibrated against known background-radiation rates, returns the time since the ceramic was last fired — that is, the age of the object as a manufactured ceramic, not the age of the clay deposit it was made from.
Reliability: TL is a robust technique on uncontaminated clay-body samples. Standard accuracy ranges from ±5% to ±15% depending on sample condition, background-radiation profile, and the calibration available for the specific clay-body type. The technique is most useful for ceramics in the range from approximately 100 years to 100,000 years old, which covers all African terracotta traditions including Nok, Sokoto, Katsina, Djenné, Ife, and Bankoni.
Forgery vectors: the documented forgery problem is NOT the TL technique itself but the material substrate. Forgery workshops operating since the 1980s in Bamako, Mopti, and northern Nigeria recompose genuine ancient sherd fragments (typically faces, hands, or other diagnostic surface elements) onto modern reconstructed bodies. A single TL sample taken from the modern body shows a recent date; a single sample from the ancient face shows a genuinely Iron Age date. Defensible authentication therefore requires multiple TL samples from different parts of the object — body, face, joints — together with thin-section petrography and physical inspection of break-edges under raking light.
Reference laboratories: Oxford Authentication (UK) and CIRAM (Bordeaux, France) are the standard commercial reference laboratories for African terracotta TL dating. Both publish methodology documentation and accept third-party verification samples. Brodie and Yates of Trafficking Culture (traffickingculture.org, open access) provide the most extensive open-access documentation of the forgery vector specific to West African Iron Age material.