Pre-restoration Characterization of biofilm on a sgraffito wall art: The need for proactive monitoring

Sgraffito is a technique of wall decor produced by applying layers of plaster tinted in contrasting colors to a moistened surface. The study focuses on a black and white sgraffito decoration attached to a cement exterior wall at the youth education center in Kibbutz Yiftach, Israel. Since its creation in 1971, the artwork has experienced weathering processes, resulting in the peeling and flaking of plaster layers, including the formation of an extensive biofilm. Before implementing a comprehensive preservation process, we conducted a study to characterize the biofilm structure and its interaction with the substrate's materials. Complementary methods, including mineral analysis, microscopic observations, and molecular methods, were used. Molecular sequencing identified five main groups of bacteria (Cyanobacteria, Actinobacteria, Proteobacteria, Bacteroidetes, and Chloroflexia) and different types of fungi. Microscopic observations revealed the attachment of microbial components to both the porous plaster and the rough cement, causing disaggregation of the construction materials. To the best of our knowledge, limited research exists on microbial biofilm characterization and activities associated with sgraffito wall art materials. Thus, this study seeks to advance the understanding of this topic and provide a foundation for the ongoing assessment of the sustainability of this distinctive wall art.