Stone biodeterioration: treatments and preventive conservation

This contribution updates the methodological approach currently applied in Europe for interventions in the field of stone conservation. Firstly, we describe the advancements in physical methods, which encompasses several already tested methods, such as Ultravi- olet rays and Laser cleaning, and new ones, such as Ice cleaning systems, Microwaves, and Heat shock treatments. Specifically, we discuss the efficacy of Heat shock treatments, which is an innovative and eco-friendly method, indicated their suitability especially against lichens and mosses colonization in wet conditions. Secondly, we describe the ad- vancements in the selection and use of biocides, which considers overall Natural biocides, such “green and blue” biocides, produced from plants or marine organisms. These biocides are safer compared to the traditional chemical ones, and that gave interesting results as regards efficacy for target species. We also provide comments about other chemical com- pounds, such as Multifunctional biocides with Self-cleaning properties, using primarily titanium dioxide. Among new products and techniques, we highlight functionalized Nano- materials, which have more pronounced characteristics compared to the same materialwithout nanoscale features, and seem to be a new challenging type of chemicals whose application is growing. The Bio-cleaning with microorganisms, such as the Cleaning of bi- ological patinas with enzymes and solvents, is also receiving attention and is getting more and more used. Long-lasting interventions with paired treatments, such Consolidants or Water-repellent products and biocides, also seem promising. Pigments, polysaccharide in- hibitors and permeabilizers with biocides, gave interesting results in the laboratory, even if the advantages of such treatments need further evaluation. Finally, for a management plan of archaeological areas or monumental sites, we underline the importance of preventive conservation strategies, and the need of further research, especially to define the ecological limits of the different biological colonizations