Synthesis and application of novel materials for cleaning and protection of historical documents

The cleaning of cultural heritage artifacts is a delicate conservation practice that aims to bring the surface to a state that resembles as close to its original status. However, cleaning is an irreversible treatment and thus requires high control and selectivity to avoid risks for the original materials. Solvent/water sensitive paper artworks are usually soiled by a wide range of contaminants, such as deposits of pollutants, grime, aged adhesives and waxy coatings, which are confined in the surface layer typically characterized by the co-presence of art media (e.g. inks, dyes and pigments). In order to avoid the drawbacks of traditional cleaning methods, here organic solvents were confined into chemical organogels specifically developed for the cleaning of paper-based artifacts. The organogels synthesized and studied during this work are based on poly(methyl methacrylate) network (PMMA), a polymer characterized by suitable features, i.e. mechanical strength, adhesiveness, optical transparency and low environmental toxicity. Diethyl carbonate (DEC) and methyl ethyl ketone (MEK) were used as solubilizing and porogenous agents during the organogels synthesis and also as loaded cleaning fluids for the removal of aged pressure sensitive tapes (PSTs) and waxes from paper-based artifacts. The physico-chemical and mechanical characterization were carried out on several PMMA formulations in order to investigate the synthesis parameters that affect the final properties of the organogels. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), gravimetric analysis, Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Small-Angle X-ray Scattering (SAXS) and rheological measurements were performed. Finally, the best performing organogel formulations were used for the cleaning of contemporary and historical artworks. The PMMA-DEC system was employed for the detachment of PSTs from Federico Fellini’s drawing entitled “Anniversario. 14 Maggio 1957-14 Maggio 1987”. The PMMA-MEK formulation was applied for the removal of wax spots from the printed book entitled “In officio et Missa solemni pro defunctis”, of the mid-19th century. The results of the cleaning treatments were checked through optical microscopy and ATR-FTIR analysis.