Novel surface-attached gels from photo-crosslinkable polyacrylamides for the cleaning of works of art

The application of gel materials in modern procedures for the cleaning of works of art has gained increasing interest in recent years due to their improved handling and control over liquid cleaning media, but remaining issues relate to control over excessive liquid volume and the avoidance of residue contamination, specifically surfactants, at the artwork surface. In the present study we introduce a novel hydrogel film system, which is covalently attached to a flexible polyethylene backing and which contains covalently bound surfactant residues in its polymer network. The hydrogel system is based on a polyacrylamide (PAM) copolymer and incorporates ethoxylate surfactant monomers derived from Triton X-100 (yielding PAMX copolymer) and Brij35 (yielding PAMB), respectively. These hydrogel film systems were either loaded with an aqueous solution containing free Triton X-100, or with an aqueous medium buffered at pH 5.0 without free surfactant. The swollen films were then applied in a similar way like sticky tape to the surfaces of aged and soiled mastic, dammar, shellac and polycyclohexanone varnishes. Detachment of the hydrogel films form the substrates led to efficient removal of soils and revealed smooth surfaces comparable to unsoiled resin. Besides adhesion of soils to the hydrogel surface, which was found to be characteristic for the surface-attached gel technology, water desorption from the swollen polymer network to the varnish surfaces was rapid without excessive liquid volume being transferred. Stereo-, optical and scanning electron microscopy, ultraviolet fluorescence imaging corroborated the large potential of the developed film systems for residue-free, liquid-minimizing cleaning applications.