A new deep eutectic solvent-based green gel for the removal of polymeric coating from mural painting

Abstract

It is challenging to extend the species of deep eutectic solvent (DES) based gels, particularly in forming non-toxic polymer gels with good mechanical properties. In this study, we propose an eutectogel system for cleaning purposes in the field of culture heritage conservation. Green gels containing ChCl-EG-GVL-PVA and ChCl-EG-PVA are produced by combining choline chloride (ChCl), ethylene glycol (EG) and polyvinyl alcohol (PVA) with or without γ-valerolactone (GVL). The crosslinking of the gels is primarily formed by ChCl-EG and PVA through hydrogen bonding. The additional green solvent GVL is compatible with the gel composition and plays an important role in cleaning. The developed gels exhibit good mechanical properties and fine microstructures, making them easy to handle and suitable for cleaning cultural relics. Therefore, the gels have been tested on a mockup coated with Paraloid B72^Ⓡ to examine their cleaning efficiency. Furthermore, the selected gel has been validated on a Yuan dynasty mural painting for the removal of aged acrylic coating. The results from both the mockup and the real case study demonstrate the effective cleaning efficiency of the ChCl-EG-GVL₂-PVA₂ gel and highlight its potential usefulness in the field of cultural heritage conservation.