Innovative method for the cleaning of water sensitive artifacts: Synthesis and application of highly retentive chemical hydrogels

Cleaning is one of the most important processes for the conservation of cultural heritage artifacts, but also one of the most delicate and potentially damaging to the original materials. Nowadays, aqueous cleaning is usually preferred to cleaning with organic solvents, because it is environmental friendly and less aggressive to artifact’s materials. However, in some circumstances, such as cleaning paper documents, easel paintings and textiles, water-based systems can be invasive. The interaction of water with the hydrophilic support favors mechanical stresses between substrate and paint layers, which can eventually lead to paint detachment or paint leaching. Water-based detergent systems (such as micellar solutions and oil-in-water microemulsions) offer several advantages in terms of selectivity and gentle removal of hydrosoluble (e.g. grime) and hydrophobic (e.g. aged adhesive) materials. The confinement and controlled release of these water-based systems is achieved through the synthesis and application of chemical hydrogels specifically designed for cleaning water-sensitive cultural heritage artifacts. These gels are based on semi-interpenetrating p(HEMA)/PVP networks. Semi-IPN hydrogels are prepared by embedding linear polyvinylpyrrolidone physically into a network of poly(2-hydroxyethyl methacrylate). Water retention and release properties were investigated. The micro-porosity was studied by Scanning Electron Microscopy. To demonstrate both efficiency and versatility of the selected hydrogels in confining the most appropriate water-based cleaning system a representative case study is presented.