Porosity characterization of old Portuguese ceramic tiles

The porosity of building materials affects their properties, such as, permeability, strength and durability. To evaluate the efficiency of a conservation treatment, the porosity of old ceramic tiles was assessed, before and after the application of Paraloid B-72. In the present study porosity data obtained through different techniques (image analysis with scanning electron microscopy, water absorption, nitrogen adsorption and helium pycnometry) is compared. As expected different techniques do not give the same results as they have distinct physical bases. However, identical trends are obtained, with the porosity decreasing along the centuries in the untreated samples and, in general, decreasing upon treatment. (C) 2011 Elsevier Ltd. All rights reserved.