On the porous surfaces are often present biological manifestations due to living organisms that develop on the surface, after that this has already undergone a degradation process derived from its exposure to the environment. Agents and pollutants present in the atmosphere, cause an increase in the porosity of the materials, with formation of roughness, cracks, accumulation of dirt and atmospheric particulate. After this first phase of alteration, some biological form of various organisms can appear: their reproductive spores and seeds can be anchored on surfaces, where they develop and multiply. This phase of their biological cycle induces the phenomena of alteration of the stone surface, transforming simple biological pollutants of the air into “biodeteriogens”.
The most common groupings of such biodeteriogens are: Algae – Lichens – Musks – Molds
Among the conditions that favor biodeterioration we can mention: the humidity rate above the norm; the environmental thermohigrometric regime; the formations of mineral salts present in the materials; the nature of some organic substances applied to materials, originally or undergoing restoration. The phenomenon of aggression and the mechanism of alteration produced by the various organisms are in function of: type of porous material; environmental exposure conditions; state of conservation of the surface (the lack of correct conservative care is evidenced by the presence of biodeteriogens).