Avaliação da eficácia de hidrofugantes e antigraffiti no Arenito Itararé

In stone heritage, the rock is exposed to the effects of weathering. There are treatment and protection products to delay this process. However, they can damage the heritage more than the weathering itself if they are not compatible with the rock. The Municipal Theater of Sao Paulo is an important building in the old center of the city. Its front facade is cladded with Itarare Sandstone, which is a very fragile rock due to the presence of smectite in its composition. This mineral degrades very easily in the presence of water. Aiming to study a means of protecting this stone against the action of moisture, two water repellents (siloxane — H1 — and oligomeric propyl siliconate — H2) were tested. Another problem that strikes urban centers is graffiti vandalism, mainly when it comes to Itarare Sandstone since it is porous and its cleaning is not totally effective. Also, the products used leave residues that harm its durability. To protect the stone from graffiti, an antigraffiti (AG) product was also tested. The tests performed were capillarity, Karsten tube, contact angle measurement, scanning electron microscope, mercury porosimetry, wetting and drying cycles, ultrasonic pulse velocity, spectrophotometry and depth of penetration. The water repellents showed similar behavior, however, H1 decreased the porosity of the rock and did not completely polymerize. The antigrafitti product darkened the rock and  changed the distribution of pores’ size.