Biotechnology applied to historic stoneworks conservation: Testing the potential harmfulness of two biological biocides

Within restoration practices, the biodeterioration is a common and hard problem, in particular on historic stonework conservation, where, together with weathering actions, enlarge porosity and increase the decay. The chemical action with biocides is the more used method to remove biological patina on monumental stone but, during the time, that approach reveal hazardous environmental and health impacts. In recent time, innovative biotechnology methods have been developed but used only to a minor extent; that is due to the less information about the interaction of the new products with stone material. The aim of the research is to propose innovative and safe bio cleaning products for historic stonework conservation and define the level of security in the interaction with stone material. The two biological biocides, that has not been investigated previously, are Natria, a Bayer products based on pelargonic acid, and New FloorCleaner, based on Bacillus species. The specimens for our research are made up from an historical stone material (earlier twenty century handmade bricks) and we used the Normal UNI 11551-1:2014, the European protocol for the evaluation of a cleaning method in the Cultural Heritage. Our results show that biocleaning products are harmless: overall, the research demonstrates the opportunity to use these products in the conservation field, for the treatment of biological patina of historical brick, because do not highlight problems and damages and are environmentally sustainable.