Aspects of biocide application on wall-paintings: report on Eurocare project EU 489, Biodecay

Wall-paintings are an integral part of a building and can never be treated in the same way as sculptures, furniture, easel paintings or other non-constructional objects. Climate control to reduce microbial attack cannot be achieved in most cases, and cleaning procedures and biocide application must be carried out. Within the framework of the EUREKA Project Eurocare, we have started investigations on the interactions of biocides with wall-painting materials such as lime, pigments, organic bindings and artificial consolidants including materials from former restorations, which may reduce the penetration of the biocide solution into the object. We are aware of the toxicity of most of the effective biocides and the risks to the object. Our investigations are therefore done in cooperation with toxicologists, restorers, chemists and biologists. The inhibiting effects of highly efficient biocides are also compared with less toxic methods such as lime water application, even if it does not kill microorganisms efficiently and inhibits recolonisation only in special cases. Our investigations are planned for the next ten years and will hopefully clarify the long-term aspects. The results can therefore lead towards a scientifically based decision-making for future wall-painting conservation.