The importance of being versatile: development of gel-based materials to clean paper artworks

Paper based artworks are very complex materials, made up of different components like cellulose, binders (starch or animal glues), fillers (allum, caolin) and inks, that during ageing undergo degradation processes leading to a decrease in paper stability and and a change in colour. Due to its complexity and fragile structure, paper is a very difficult media to restore also because wet cleaning, a necessary step during paper restoration process, is performed commonly by water bath that can cause swelling of fibres and dissolution of several components. Recently, to limit disavantages, the use of opportune hydrogel like rigid Gellan gel as alternative cleaning method, has been assessed. This treatment, unfortunately, is not sufficient to remove specific contaminants like old glues or foxes. In this work we have investigated about the possibility of using opportunely modified hydrogels to solve heterogeneous problems. To this end, for example, we have prepared Gellan hydrogel loaded with hydrolytic enzymes to remove old glues. Moreover, as Gellan hydrogel itself, is not able to clean hydrophobic contaminants, we have performed experiments by preparing a “mixed Gellan gel” carrying opportune polimeric surfactants. In this system, the enzyme (or surfactant) works as selective cleaning agent, while the gel plays the role of support and removal matrix for the contaminants. To assess the effectiveness and safety of the proposed cleaning method on the several samples under examination we have employed a several mesurements, using UV-Vis and IR spectroscopy, rheology, scanning electron microscopy high-performance liquid chromatography analysis and pH measurements.