Mortar and surface dating with Optically Stimulated Luminescence (OSL): Innovative techniques for the age determination of buildings

In this work the results of a dating study on bricks and mortars using both Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are shown. The samples came from the outside walls of the Certosa di Pavia, located in northern Italy and independently dated (XVII-XVIII century). TL dating, applied to bricks using the fine grain technique, allowed to determine the time of manufacture of the bricks (XII century), that resulted therefore re-used. To circumvent this problem the application of two innovative dating techniques, OSL surface dating and mortar dating, was attempted. The first was applied to the light-shielded surfaces of bricks and allowed to successfully determine the edification of the wall (XVII century). Mortar dating gave instead severe age overestimation: the results obtained on coarse grain quartz with the SAR technique both on multi-grains aliquots and with single-grain analyses were highly dispersed indicating an incomplete bleaching of the quartz grains. The shine-down curves were in fact characterized by the absence of the so-called fast component, as confirmed by Linear Modulated OSL technique.