Green strategies for the cleaning of works of art setting up of an analytical protocol for the evaluation of cleaning

In last decades, the safety of both artworks and restorers during cleaning operations, has been the subject of many research works, aimed at the development of gel-systems that confine the solvent action to the very surface thus preventing its absorption into the paint layers and minimizing operators’ exposure. In this research work, a totally sustainable approach has been presented for the cleaning of artworks. In particular new organogels made of bio-compatible components, were evaluated as cleaning tool for the removal of paint varnishes. The gels consist of a polymer derived from renewable bio-materials, poly(-3hydroxybutyrrate), and different green solvents (γ-valerolactone GVL, ethyl lactate EL, dimethylcarbonate DMC). These gels, previously characterized in order to investigate thermal and mechanical properties, were tested for the removal of natural and acrylic varnishes over different binding medium (linseed oil, egg and glue).The gels were first tested on painting mock-ups, not aged and aged, then validated on real paintings. Their cleaning capabilities were compared to methods traditionally employed in restoration (e.g. dimethyl sulfoxide, benzyl alcohol, acetone, carbopol-gel). A specific protocol of cleaning evaluation was designed for assessing varnish removal capability, residues releasing and solvent retention by means of Optical Microscope observations of paint cross sections in visible and ultraviolet light, μFTIR-Attenuated Total Reflection surface analyses and Head Space-Solid Phase Micro Extraction coupled with GC-MS analyses. These new totally safe and biodegradable organogels demonstrated good varnish cleaning capabilities that, in conjunction with their easy preparation, use and waste, represent a “green” and safe approach for both paintings and painting restorers.