Cleaning testing of nineteenth-century plaster cast reconstructions with thin polyacrylamide-based surface attached gels

Abstract

Abstract 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.