Restoration of paper artworks with microemulsions confined in hydrogels for safe and efficient removal of adhesive tapes

Significance From Dead Sea Scrolls to Federico Fellini and Lucio Fontana drawings, pressure-sensitive tapes (PSTs) have been used as adhesive fasteners or as part of temporary conservation treatments that frequently became permanent. Their safe and efficient removal poses ethical and aesthetic questions: Adhesive tape residues damage the paper substrate and, due to discoloring, prejudice the artwork enjoyment and conservation. Selective removal without affecting the underlying support is challenging and often impossible. We tackled this issue from a physicochemical and a colloidal perspective, by designing a system where nanosized solvent droplets are confined within a hydrogel. This method has the potential to revolutionize the approaches used so far in the removal of PSTs and coatings from a plurality of materials. The presence of pressure-sensitive tapes (PSTs) on paper artworks, either fortuitous or specifically applied for conservation purposes, is one of the most frequent and difficult issues encountered during restoration. Aged PSTs can damage or disfigure artworks, compromising structural integrity, readability, and enjoyment. Current procedures are often inherently hazardous for artistic media and paper support. Challenged by the necessity to remove PSTs from a contemporary and an ancient drawing (20th century, by artists da Silva and Hayter, and a 16th-century drawing of one figure from the Sistine Chapel by Michelangelo), we addressed this issue from a physicochemical perspective, leveraging colloid and interface science. After a characterization of the specific PSTs present on the artifact, we selected a highly water-retentive hydrogel as the host of 23% wt/wt of “green” organic solvents uniformly dispersed within the gel in the form of nanosized droplets. The double confinement of the organic solvent in the nanodroplets and into the gel network promotes a tailored, controlled removal of PSTs of different natures, with virtually no interaction with the solvent-sensitive artwork. This noninvasive procedure allows complete retrieval of artwork readability. For instance, in the ancient drawing, the PST totally concealed the inscription, “di mano di Michelangelo” (“from Michelangelo’s hand”), a possibly false attribution hidden by a collector, which is now perfectly visible and whose origin is currently under investigation. Remarkably, the same methodology was successful for the removal of aged PST adhesive penetrated inside paper fibers of a drawing from the celebrated artist Lucio Fontana.