Thermoluminescence Analysis of the Clay Core of Bronze Statues: A Re-Appraisal of the Case Studies of Lupa Capitolina and Other Masterpieces in Rome

In this work, we present some new results in applying thermoluminescence (TL) dating to the clay core of bronze statues. This is very important, due to the impossibility of directly dating a metal. Very few cases of indirect dating of clay cores by TL are reported in the literature. We re-considered three cases of dating of clay core from important bronzes in Rome. The parameters to be considered were not easy to calculate in the case of the Lupa Capitolina. However, its traditionally reported Etruscan origin is definitely ruled out, even if the accuracy in the dating is too low to precisely propose a date of the casting. The comparison with radiocarbon results shows good agreement for a Medieval dating. Two other bronze statues were analysed in order to date their casting by TL; a horse from Musei Capitolini resulted to have been cast in the Greek classical period, excluding its casting in the Rome imperial period. A third study shows that, in particularly favourable situations, TL dating of clay core can give rather precise results. This is the case where in the clay core are present materials that behave like good dosimeters, as generally happens in dating ceramics. Furthermore, the possibility of measuring all the parameters influencing the calculation of the dose rate is essential; both the external radiation sources and the radiation reduction by the water content must be taken into account. This was the case of Saint Peter in the Vatican that turned out to be a cast from the beginning of the XIV century.

Thermoluminescence Analysis of Bricks from the so-called Arch of Ali Shah

The application of Thermally (TL) and Optically (OSL) Stimulated Luminescence on bricks used as building material can answer questions regarding the chronology of historical buildings. The remarkable historical reports of the “largest ever made brick vault” known as the Arch of Ali Shah (14th century) invoke the image of a gigantic structure adjoining the u-shaped brick monument in Tabriz. However, there is new scientific data that has led us to consider an alternate hypothesis regarding this monument that contradicts the traditional views of scholars. The attribution of this controversial building to Ali Shah, the great vizier of the Ilkhanid court, has long been considered an historical fact by scholars. To better understand the evolution of this unique structure, thermoluminescence (TL) was used to propose a relative dating for its construction. Surprisingly, the results yielded dates of 512±20, 514±27 and 517±21 AD (TL age, equaling 17th century), indicating that the u-shaped structure was built some 200 years after the Ilkhanid era. These dates, supplemented with historical context and architectural evidence, leads to the conclusion that it was used as a separate building before being integrated into the older building, thereby converting the entire complex into a formidable fortification. The remains of the so called Arch of Ali Shah are clearly of a later date, characterizing a completely different architectural style than those of the Ilkhanid period.