Historical mortar: luminescence from fine grain quartz

Within the framework of a research programme aimed at the chronological reconstruction of the structures belonging to the architectonic complex of San Francesco alla Collina of Paternò (Catania, Italy), a procedure was carried out using thermoluminescence (TL) and optically stimulated luminescence (OSL) dating, respectively on terracotta bricks and mortar from the same sampling points. The primary methodological aim was to extend the application of luminescence dating techniques to mortar from historical buildings. Because the TL dating method dates the last firing of bricks, it offers a terminus post quem: the results give the period in which they were manufactured. The possibility that these bricks could have been reused complicates the interpretation of data. Contextual historical mortar and terracotta bricks dating could resolve this problem giving a more reliable date for the construction. We report here the results obtained on bricks, undergone the standard fine grain technique, and on mortar, whose chemical-physical preparation required some modifications to this protocol verifying the results step by step. A methodology was thus established to allow, by IRSL (InfraRed Stimulated Luminescence) measurements, the verification of the feldspar component reduction and the acquisition of an enriched quartz phase that underwent OSL dating. The comparison of TL and OSL ages showed a good agreement thus supporting, in this case, the potential of the methodology for mortar dating