Organic solvents confined in poly (ethyl methacrylate) based organogels for the removal of unwanted materials from works of art

Aged pressure sensitive tapes (PSTs) are widespread on paper artefacts due to their large use for mending, mounting, and framing operations. Their removal is mandatory due to associated degradation processes, but all common restoration techniques involve some drawbacks. In this work a new methodology is proposed: the embedment of proper solvents into gels that can be directly applied on PSTs surfaces. The tape detachment is achieved by solvents penetration in the backing and the later swelling of the underlying adhesive; in this way controlled solvent-artwork contact and decreased solvents evaporation are ensured. According to solubility parameters of PSTs compounds, we focused on diethyl carbonate (DEC) as cleaning fluid, a green solvent inert towards most common dyes. Its affinity to acrylic polymers addressed us to test DEC confinement in poly (ethyl methacrylate) networks: cross-linked chemical gels were synthesized since their mechanical strength prevents from residues left on substrates; blended systems, realized by embedding poly (ethylene glycol) chains, allowed significant improvements in gels flexibility. Physicochemical characterization on selected formulations was carried out by gravimetric measures, calorimetry, rheology, and IR spectroscopy. The ability of gels in retaining other solvents useful in the restoration practice was also tested. Gels applicative features were evidenced by testing representative samples: Confocal Microscopy, IR spectroscopy, pH measures, and thermogravimetry were performed. The developed gels were finally used in real case study: the interventions on drawings by Fellini, Haring, and Vedova, on a XIX century Divina Commedia, and on photographic and cinematographic films are here presented.