“White” Crusts on Recent Buildings
Materials applied in buildings, sculptures and other civil engineering, architectural or artistic works can be affected by coatings of neoformation products, namely salts. Carbonate rich (typically calcite) coatings are common in recent constructions. They generally have a visual impact (frequently present a vertical streaking pattern and it could be argued that the aesthetic effect of white crusts on dark-coloured stones is similar to that of black crusts on light-coloured stones). The thickness and extension that can be achieved in some cases can be considered an important defacement process that develops in relatively small periods of time. There are evidences that in some situations the process might be recurrent with time. Its chromatic evolution with time could also contribute to increasing heterogeneity with aesthetic consequences. An interesting question regarding these crusts is the possible contribution of certain building materials to its formation, materials that will be, in this way, potential pollution sources that might affect other building materials.
Luís Guerra ROSA and Fernanda MARGARIDO
C. Alves "“White” Crusts on Recent Buildings", Materials Science Forum, Vols. 636-637, pp. 1300-1305, 2010