The Susceptibility to Biodegradation of Some Consolidants Used in the Restoration of Mural Paintings

Abstract

This study evaluated both the possible fungal metabolites involved in the degradation of the commercial consolidant known as Paraloid® B72 and the national artisanal consolidant named transparent dispersion of casein and the deteriorative potential of melanised fungi. Fungi were found to have the capacity to produce organic acids, proteases and esterases when they grow on consolidants, which can be used as nutrients. Mycelia produced by melanised fungi affected the appearance, as well as the integrity, of consolidants applied on painted experimental models and fragments of frescoes. In treatment trials with biocides (Biotin R®, Biotin T® and Preventol® RI 80), the morphology of the consolidants, as well as the vitality of the fungi, were assessed 30 days after the inoculation with melanic fungi. Direct observation, optical microscopy, colourimetry and microbiological analysis highlighted the degradation of the consolidants by fungi and their acquired resistance after biocidal treatments. Biotin R® applied by brushing on the surface of the consolidants proved to be the most effective treatment, followed by Biotin T®. Considering the overall results for both Paraloid® B72 and transparent dispersion of casein, use of Biotin R® applied by brushing is recommended for preventive conservation.

Experimental Study and Effectiveness Evaluation on the Rapid Antiquing of Red Sandstone in Ancient Buildings Restoration

“…First of all, the red sandstone's antiquing in ancient buildings is different from the cultural relic restoration. Cultural relic restoration is ultimately similar to the fresco, which is the structure of the final restoration while the ancient building restoration is mostly the wall, which is the repair of missing parts of appearance [11,12]. Its surface structure, crack, and concave and convex sense do not have a uniform shape, therefore, when antiquing ancient buildings, it is not only necessary to be similar in style and texture but also to achieve a sense of irregularity of "Like but not the Same", which is exactly the difficulty for rapid antiquing in ancient buildings [13,14].…”

Brackish and Hypersaline Lakes as Potential Reservoir for Enzymes Involved in Decomposition of Organic Materials on Frescoes

“…Cultural heritage buildings and artifacts require restoration, which brings them as close as possible to the original shape and aspect by consolidation and cleaning. Traditional conservation treatments are gradually replaced by green technologies (less aggressive, more specific, and more sustainable), including bioconsolidation, protection, and biocleaning [28][29][30][31] based on living microorganisms or their metabolites. Bioconsolidation is performed with selected carbonatogenic bacteria or by stimulation of relevant autochthonous microorganisms, including fungi [30][31][32].…”

“…Bioconsolidation is performed with selected carbonatogenic bacteria or by stimulation of relevant autochthonous microorganisms, including fungi [30][31][32]. The biocleaning of various surfaces is based on applying living microorganisms for removing inorganic deposits (e.g., sulfate-reducing bacteria such as Desulfovibrio desulfuricans, nitrite-reducing bacteria such as Pseudomonas stutzeri), or hydrolytic enzymes for removing of organic materials (delivery system + hydrolytic enzymes such as proteases, lipases) [28,29,33,34]. To our knowledge, there has been no research on the isolation of fungi from brackish and hypersaline environments to be tested in order to highlight their role as decomposers of organic deposits on mural surfaces affected by salts.…”