Varnishes with Biocidal Activity: A New Approach to Protecting Artworks

Abstract

Keeping agents that cause biodeterioration under control is a common task in restoring and conserving artworks. However, there are very few studies, specifically those concentrating on pictorial works, that provide solutions compatible with the complex mix of organic and inorganic materials to be found in such cultural assets. This study aims to use biocide products that are commonly used in this field (benzalkonium chloride, o-phenylphenol, and tributyltin naphthenate) and which are associated with natural varnishes with a long tradition in artistic practices, in order to protect paintings and polychrome sculptures from environmental fungi and bacteria without altering the original materials or the visual appearance of the artworks. The effectiveness or innocuousness of the treatments was tested chemically and visually via optical microscopy, gas chromatography–mass spectrometry (GC-MS), and a multidimensional scaling analysis (MDS); the treatments produced good results as regards the inhibition of microbial growth and scarce interaction with the artistic materials being studied.

Degradation Potential of Xerophilic and Xerotolerant Fungi Contaminating Historic Canvas Paintings

“…Traditionally, natural resins such as terpenoid resins, mastic, sandarac, copal, dammar, elemi, or rosin resins are used as varnishes for canvas paintings and are considered less acceptable for biodeterioration [34][35][36]. Various mixtures can also be used, such as terpenoid resin-based oil varnishes, which consist of a drying oil (linseed oil), a diterpenoid resin (colophony), and a triterpenoid resin (mastic) [34].…”

“…In traditional painting, they are usually applied after dissolving natural resins in oil, such as vernice comune (mixture of colophony/oleoresin and linseed oil), or by dissolving terpenoid resins in spirits of wine and turpentine [33]. There are rare reports of biodegradation of natural resins by bacteria and fungi [34][35][36].…”

New frontiers review of some recent conservation techniques of organic and inorganic archaeological artefacts against microbial deterioration

“…Traditional chemical products like benzalkonium chloride, o-phenyl phenol, and tributyltin naphthenate can be combined with natural varnishes to preserve artwork against environmental fungus and bacteria without affecting the materials’ inherent properties or the way the pieces look ( Romero-Noguera et al, 2020 ). Eldeeb et al (2022) used dry cleaning and disinfection as conservation techniques for the most significant photographic prints from the late 19th century are albumen prints which consist primarily of two layers: the paper support (cellulose) on the top and the image layer on the bottom (image silver particles embedded in an albumen binder layer).…”

“…The most effective combination was biocide and water repellent ( Wang et al, 2021 ). Additionally, the combination of a conventional chemical substance with natural varnishes, such as tributyltin naphthenate, o-phenyl phenol, and benzalkonium chloride, should help shield polychrome sculptures from environmental fungi and bacteria without affecting the original materials or the visual appeal of the artworks ( Romero-Noguera et al, 2020 ).…”

Editorial for the Special Issue “Microbial Communities in Cultural Heritage and Their Control”

“…In other cases, the association of a traditional chemical product such as benzalkonium chloride, o-phenylphenol, and tributyltin naphthenate with natural varnishes should be useful to protect paintings and polychrome sculptures from environmental fungi and bacteria without altering the original materials or the visual appearance of the artworks [9].…”