Poly(vinyl alcohol)/poly(vinyl pyrrolidone) hydrogels for the cleaning of art

Abstract

The cleaning of modern and contemporary paintings is a delicate and challenging operation. Many contemporary paintings exhibit rough, clotted and pitted surfaces, where the removal of soil is difficult. Gels are among the most efficient tools to achieve controlled and efficient cleaning of works of art. However, most gels used in the conservation practice are too rigid to adapt rough surfaces, or too mechanically weak to be removed without leaving polymer residues. Several formulations of physically cross-linked poly(vinyl alcohol) (PVA)-based hydrogels, obtained by cast-drying or freeze-thawing of aqueous polymeric solutions, were formulated and characterized. The viscoelastic properties, porosity, and crystallinity of the gels were studied, along with the behavior of water inside the polymeric network. It was shown that the properties of the gels were improved through blending with poly(vinyl pyrrolidone) (PVP). The most promising gel formulation, in terms of mechanical properties and water retentiveness, was assessed for the removal of soil from an alkyd painting mock-up. A traditional gel, gellan gum, was also tested as a reference system. The effectiveness of soil removal was investigated by 2D Fourier transform infrared (FTIR) microscopy, using a Focal Plane Array (FPA) detector. In conclusion, it was shown that the newly developed formulation grants the residue-free removal of soil from rough and irregular artistic surfaces, overcoming the limits of traditional cleaning methods.

Facilitating the conservation treatment of Eva Hesse’s Addendum through practice-based research, including a comparative evaluation of novel cleaning systems

“…The Nanorestore Gel ® Peggy series 10 was specifically developed within the NANORESTART project for the cleaning of contemporary works of art with textured or irregular surfaces. These gels are opalescent, physical hydrogels based on a poly(vinyl alcohol) polymeric network, synthesised through a freeze-thaw process [39][40][41][42]. Among the options available, Nanorestore Gel ® Peggy 5 consists of a blend of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) polymers, where the PVP provides enhanced retention properties [40].…”

“…These gels are opalescent, physical hydrogels based on a poly(vinyl alcohol) polymeric network, synthesised through a freeze-thaw process [39][40][41][42]. Among the options available, Nanorestore Gel ® Peggy 5 consists of a blend of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) polymers, where the PVP provides enhanced retention properties [40]. Nanorestore Gel ® Peggy 6 is made from PVA alone and is more flexible and elastic than Nanorestore Gel ® Peggy 5, with potential for enhanced conformation to moderately textured surfaces [39,42].…”

“…Due to the difficulties experienced with keeping the Nanorestore Gel ® Peggy series in contact with the ropes, a new set of gels, temporarily known as TT gels, were synthesised for further evaluation. This series consisted of adaptations of the Nanorestore Gel ® Peggy 5 (PVA/ PVP) prepared by either changing the ratio between the two copolymers, increasing the number of freeze-thaw cycles, and/or the synthesis parameters [40,42], to offer greater stickiness to aid in wrapping the gels around the ropes so they did not require additional clamping. The TT gels, loaded with deionised water only, were tested on the range of rope mock-ups (Additional file 1: Table S4), to evaluate their suitability for Addendum and compare their physical and mechanical properties with the Nanorestore Gel ® Peggy series.…”

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

“…In the last decades, NSFs have proved to be highly efficient in the swelling and removal of hydrophobic coatings [8][9][10][11][12][13][14][15][16], as they work through a removal mechanism that, for high molecular weight substances, such as polymers, is based on dewetting and detachment, thus allowing a more controlled surface cleaning with respect to traditional solvent chemistry [17][18][19][20][21]. As mentioned, the use of aqueous fluids on modern oil paints requires special attention, and an optimal strategy is thus to confine cleaning fluids in retentive gel matrices, minimizing the risks to the artifacts [22][23][24][25][26][27][28][29][30]. The physicochemical characterization of the combined gel-NSF cleaning system included the interaction of the NSF with the gel and its diffusion inside the gel network, which were investigated using Confocal Laser Scanning Microscopy (CLSM) and Fluorescence Correlation Spectroscopy (FCS).…”

Characterization of polyvinyl alcohol-borax/agarose (PVA-B/AG) double network hydrogel utilized for the cleaning of works of art

“…For instance, poly-2-hydroxyethyl methacrylate/polyvinyl pyrrolidone, polyvinyl alcohol/polyvinyl pyrrolidone, polyvinyl alcohol-borax blended with polyethylene oxide¸ and polyvinyl alcohol-borax complexed with carbomer. In all the above-mentioned hydrogel examples, the addition of the second polymer was done to optimize the properties of the resulting hydrogel to meet the criteria of speci c cleaning needs [30][31][32][33].…”