Cleaning testing of nineteenth-century plaster surface models with thin polyacrylamide-based gel layers attached to flexible polyethylene films

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.