Surface decontamination is of general concern in many technical fields including optics, electronics, medical environments, as well as art conservation. In this respect, we developed thin copolymer networks covalently bonded to flexible polyethylene (PE) sheets for hydrogel-based cleaning of varnished paintings. The syntheses of acrylates and methacrylates of the surfactants Triton X-100, Brij 35, and Ecosurf EH-3 or EH-9 and their incorporation into copolymers with acrylamide (PAM) and N-(4-benzoylphenyl)acrylamide are reported. Photocrosslinked polymer networks were prepared from these copolymers on corona-treated PE sheets, which can be swollen with aqueous solution to form hydrogel layers. The cleaning efficacy of these PE-PAM hydrogel systems, when swollen with appropriate cleaning solutions, was evaluated on painting surfaces in dependence of the PAM copolymer composition and degree of crosslinking. Specifically, soil and varnish removal and varnish surface solubilization were assessed on mock-ups as well as on paintings, indicating that even surfactant-free cleaning solutions were effective.

This paper explores the cleaning efficacy of polyethylene-supported 15-min photo-crosslinked poly (acrylamide-co-benzophenone) surface-attached gels (SAGs) on gypsum plaster surface models inspired by nineteenth-century casts. Cleaning tests were performed on plaster surface models with and without organic and inorganic coatings, which had been exposed to accelerated ageing by heat, humidity, and light after artificial soiling. The specific types of SAG systems were selected based on their water loading and dehydration capacities. The SAGs were loaded with customized solutions and applied on the plaster models for one minute. Cleaning efficacy was evaluated with visible reflectance, UV fluorescence photography, scanning electron microscopy, colorimetry, UV/Vis spectrophotometry, glossimetry, high resolution 3D microscopy, attenuated total reflection Fourier transform infrared spectroscopy and 2D Fourier transform infrared imaging. The SAGs provided fast and minimal wetting of the substrates, prevented excessive liquid spreading and allowed the effective liquid contact with the soiled gypsum plaster surface. A striking removal of soils from the gypsum plaster surface models was observed, which suggests convenient application of the SAG systems for the cleaning of historical plaster objects.

This paper explores the cleaning efficacy of polyethylene-supported 15-minute photocrosslinked poly(acrylamide-co-benzophenone) (PE-PAM15) surface-attached hydrogels on gypsum plaster reconstructions of nineteenth-century casts. After temperature-humidity and light exposure and after artificial soiling of the plaster plates, tests were performed directly on the surface, with and without organic and inorganic coatings. The surface-attached hydrogels were selected according to water loading and dehydration capacity. The PE-PAM15 systems loaded with aqueous solutions were applied on the plates for one minute. Upon lifting the gels, cleaning efficacy was evaluated with Visible Reflectance, UV Fluorescence, Scanning Electron Microscopy, Colorimetry and UV/Vis Spectrophotometry, Glossimetry, HR 3D Microscopy, Attenuated Total Reflectance- and 2D Fourier Transform Infrared Imaging. Satisfactory removal of soils from the gypsum plates is reported. The PE-PAM15 obtained fast and minimal wetting of the substrates, prevented excessive liquid spreading and the slow liquid diffusion onto the water-sensitive gypsum plaster. A minor dissolution and recrystallization of the plaster could have been introduced and was identified by an insignificant change of roughness and gloss. The cleaning tests showed promising results, suggesting that further development of this method could unfold novel approaches for the cleaning of historical plaster surfaces.