ABSTRACT
Encrustation is formed on exposed marble as a result of various physical and chemical processes which occur between the stone surface and atmospheric pollutants (Gauri & Holdren 1981). Black crusts of varying morphological characteristics and chemical composition arise from the interaction of stone with atmospheric agents, such as SO2, and dry or wet deposition of atmospheric particles. According to the wetting type of stone surface various intermediate crust formations have been referred up to now in the literature (Amoroso & Fassina 1983). Further, the physicochemical processes determining the origin and growth of deteriorating crusts are associated with the type of environmental attack and the stone surface.
