Microbial recolonization of artificial and natural stone artworks after cleaning and coating treatments

Historical stone artworks are susceptible to damage in many environments. Biodeterioration caused by lichens and biofilm-forming microorganisms on these artworks has gained growing attention in the field of cultural heritage conservation. The current approach is focused on planned removal of lithobionts whenever they cause objective damage and/or structural impairments to the substrate. Cleaning may sometimes be followed by the application of organic and/or inorganic products for protection and consolidation of the artworks. The lithobiontic recolonization after cleaning and coating treatments is considered as one of the most challenging subjects nowadays. It is expected to occur in outdoor conditions, particularly on porous substrates, in shaded areas, and in areas that remain moist over time. Two aspects connected to this topic are the recolonization of surfaces after removal of biofilms and lichens, and the recolonization of cleaned surfaces treated with consolidants and/or water repellents. This paper reviews the scientific advances of the last two decades on i) recolonization of artworks, and ii) interaction between synthetic polymers and lithobionts.