Staining tests for granitic stone conservation (book chapter)

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Abstract:

Although building stones used in historic and modern buildings and monuments may have unlimited durability if adequate conservation methods are applied, the great diversity of their nature often impairs the choice of the most suitable maintenance or cleaning procedures. Aiming at to contribute to the improvement of stone conservation, this paper presents a laboratory simulation for the anticipation of possible alterations in the stone surface when in contact to chemical reagents typically used in cleaning products, both domestic and professional, as ammonium chloride, sodium hypochlorite, hydrochloric acid and potassium hydroxide. Tests indicated that hydrochloric acid was the most aggressive among the selected substances, usually causing intensive discoloration or bleaching of the selected granitic rocks (granites, charnockites etc.). In white granite, specifically a garnet granitic gneiss, the effect was a red-orange staining, rust-like. Thus, the results also reinforced the great susceptibility of the Fe element to chemical attack. Finally, it is emphasized the recommendation to preceded by tests any application of cleaning products, to ensure physical and aesthetics stone preservation.


Reference:
FRASCÁ, Maria Heloisa Barros de Oliveira; NAVARRO, Fabiano Cabañas; QUITETE, Eduardo Brandau. Staining tests for granitic stone conservation. In: LOLLINO, Giorgio et al. Engineering geology for society and territory. London: Springer, 2015. v.8: Preservation of cultural heritage. p.511-514. (International Congress of the International Association of the Engineering Geology,12., 2014, Torino)

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