Twin-chain polymer hydrogels based on poly(vinyl alcohol) as new advanced tool for the cleaning of modern and contemporary art

Abstract

Conservation of our cultural heritage is fundamental for conveying to future generations our culture, traditions, and ways of thinking and behaving. Cleaning art, in particular modern/contemporary paintings, with traditional tools could be risky and impractical, particularly on large collections of important works to be transferred to future generations. We report on advanced cleaning systems, based on twin-chain polymer networks made of poly(vinyl alcohol) (PVA) chains, semiinterpenetrated (semi-IPN) with PVA of lower molecular weight (L-PVA). Interpenetrating L-PVA causes a change from gels with oriented channels to sponge-like semi-IPNs with disordered interconnected pores, conferring different gel (and solvent) dynamics. These features grant residue-free, time efficient cleaning capacity and effective dirt capture, defeating risks for the artifact, making possible a safer treatment of important collections, unconceivable with conventional methods. We report as an example the conservation of Jackson Pollock’s masterpieces, cleaned in a controlled way, safety and selectivity with unprecedented performance.

Twin-Chain Polymer Networks Loaded With Nanostructured Fluids for the Selective Removal of a Non-Original Varnish From the Picasso’s “L’atelier” at the Peggy Guggenheim Collection, Venice

“…They are flexible and elastic, and their controlled release of uploaded fluids grants the possibility of varying the fluids contact time with the paint surface, controlling the interaction between solvents and paint layers. These features have already established the TC-PNs as suitable tools for the cleaning of modern and contemporary art in previous case studies [1,36,37], which proved that their synthetic process can be feasibly tuned and changed in order to vary the gels' characteristics and to adapt them to specific needs. The loading of the gel with the NSF was obtained simply by immersing a piece of gel in an excess of NSF for at least 24 hours, according to our previous experiments with these systems.…”

“…Besides, the presence of MEK induces a decrease in the aggregation number and size of the surfactant micelles, thus an increase in the total surface area of the micelles, which boosts their surface activity [49]. The fitting model for the neat TC-PN was chosen, according to published papers on similar systems [1,51,52], as the sum of two superimposed contributions to the scattered intensity, due to fixed polymer junctions (i.e. the solid-like tie points of the network) and to the polymer chains the gel water-rich environment, respectively.…”

“…This represents is a new approach as opposed to the semi-interpenetrated networks (semi-IPNs) previously developed at CSGI, which used two different types of polymers. It was shown that the addition of the lower molecular weight PVA changes the porosity and mechanical properties of these gels as compared to single-PVA gels, and the cleaning efficacy is improved [1]. These TC-PNs proved to be advantageous systems for the cleaning of paintings, owing to their mechanical properties, retentiveness, ability to remove soil, and the controlled cleaning process.…”

“…These TC-PNs proved to be advantageous systems for the cleaning of paintings, owing to their mechanical properties, retentiveness, ability to remove soil, and the controlled cleaning process. The TC-PNs were used for the first time to confine aqueous solutions and remove dust and dirt from the two aforementioned works by Pollock [1], as part of a conservation program on the eleven works by Pollock at the PGC (for overview of the program https://www.guggenheim-venice.it/en/art/conservation/case-studies/pollock/). The TC-PN used on the Pollock paintings had a tailored formulation in order to adapt to the specific requirements of those works, but served as a prototype for a series of multipurpose gels, which were formulated to target typical cleaning cases and named Nanorestore Peggy Gels® and Nanorestore Peggy Gums®, after the PGC.…”

“…agar, gellan), as well as rigid chemical gels such as semi-IPNs of poly(2-hydroxyethyl methacrylate) and poly(vinylpyrrolidone) (pHEMA/PVP) [4]. However, rigid gels are not able to adapt to textured surfaces, such as those of modern and contemporary paintings by Picasso, Pollock, Van Gogh, and others, characterized by both the presence of high brush strokes and the usage of sensitive paints, sometimes squeezed directly from the tubes to the canvas [1]. In view of the above issues, one of the main goals in the cleaning of modern and contemporary paintings is the development of novel classes of gels, that are able to adhere to textured surfaces and to minimize the interaction between cleaning fluids and the paint surface thanks to: 1) effective confinement of solvents, i.e.…”