An empirical model of the sunlight bleaching efficiency of brick surfaces

Subsamples were cut from the inner core of a XV century brick: the newly created surfaces, never exposed before, were put under daylight for different times (60 s - 1 year), and their residual OSL/IRSL signal was monitored as a function of both depth and exposure time. After one year of exposure, the first external layer (0-0.5 mm) resulted partially bleached with a 20% residual. It is observed that the models proposed so far to describe the luminescence depth profile in rocks are not applicable for the bricks. The use of a newly developed numerical model gives the possibility to evaluate the bleaching effectiveness of solar exposure for archaeological bricks.