Abstract
Cleaning is one of the most important and delicate operations in the conservation of cultural heritage, and, if not correctly performed, may irreversibly damage works of art. The removal of aged or detrimental polymeric coatings from works of art is a common operation in conservation, and nanostructured fluids (NSFs), such as aqueous swollen micelles and oil-in-water (o/w) microemulsions, are used as an alternative to non-confined organic solvents that pose a series of non-negligible drawbacks. NSFs effectiveness in removing polymeric coatings has been thoroughly demonstrated in the last decades, while their cleaning mechanism is still under investigation. The present work deepens the knowledge on the removal mechanisms of NSFs, studying the interaction of a four-component NSF with four different types of acrylic and vinyl polymer films cast from solutions or aqueous polymer latexes on three substrates (glass, marble and polystyrene) with different hydrophilicity and wettability. NSFs were applied either as non-confined or confined in cellulose poultices (traditionally employed by conservators), or in highly retentive chemical gels, observing the influence of the confining matrix on the removal process. It was found that the NSF/polymer film interaction is greatly dependent on the film structure and composition. Films formed from solvent solutions can be swollen by water/organic solvents mixtures or dewetted when a surfactant is added to the cleaning fluid; films formed from polymer latexes, on the other hand, are generally swollen even just by water alone, but poorly dewet. The substrate also plays an important role in the removal of polymer films formed from solutions, for instance the removal of an acrylic polymer from polystyrene could be achieved only through highly selective cleaning using NSF-loaded chemical hydrogels. These results can be key for conservators, providing innovative solutions to face new challenges in art preservation.
Highlights
Cleaning of works of art generally consists in the selective removal of materials that promote the degradation of the artifacts or alter their readability and appearance
It can be noticed that the acrylics are more hydrophobic than the vinyls, and the films deriving from polymer latexes are more hydrophilic than those coming from solutions
This study focused on unveiling some key aspects of the nanostructured fluids (NSFs)/polymer coatings interaction depending on several different factors: (i) the chemical nature and, hydrophilicity of the substrate; (ii) the chemical nature and physical structure of the polymeric films to be removed; (iii) the influence of the application methodology on the cleaning outcome
Summary
Cleaning of works of art generally consists in the selective removal of materials that promote the degradation of the artifacts or alter their readability and appearance. Among these materials, aged or detrimental polymeric coatings are often found on works of art, and their removal is a common operation in art conservation. Other cases include the removal of aged pressure sensitive tapes from paper artworks (Bonelli et al, 2018), or of discolored and cracked varnishes from paintings (Burnstock and Kieslich, 1996; Baglioni et al, 2018a)
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