The blackening of stone exposed to an urban environment in two Spanish cities was studied. Samples of limestone, dolomite, marble and granite were placed in positions which were either exposed or sheltered from direct rainfall in Burgos and Oviedo, which have Continental and Atlantic climates, respectively. Colour changes caused by surface deposits were monitored by measuring the lightness, L*. The limestone samples exhibited a linear relationship between blackening and the square root of exposure time, the soiling of sheltered samples being more severe than that of marble and granite. The soiling was related to colour, pore structure and surface characteristics. The soiling of the exposed samples was also dependent upon rainfall. 24 refs.
Primary author(s): Grossi C M;Esbert R M;Diaz-Pache F;Alonso F J
Vol.38, No.1, January 2003, p.147-159