Melbourne is renowned for its active street and urban art scenario, which has artistic, social, aesthetic and economic value. The murals, as well as other heritage objects, often get tagged and require selective removal of the new spray paints with complex formulations without damaging paint layers underneath. The workshop Hydrogels in Conservation, taught by conservation scientist Mathew Cushman, and organised by Cesmar7 (Centro per lo Studio dei Materiali per il Restauro) in Reggio Emilia, Italy, from 28 to 30 September 2023, provided me with new tools and material-based knowledge that better equip me to face these ongoing conservation issues. This was made possible by the generous scholarship provided by the Australian ArtsNational Patricia Robertson Fund in 2023.
In the workshop, traditional and recently implemented hydrogels were taken into consideration, some of which were: xanthan gum, agar-agar, agarose, gellan gum, gelatine, curdlan, Nanorestore Gel® Peggy 6, borax gel and PVA, used both in pure form as well as in mixture such as PVA-agar-borax. Different preparation methodologies, percentages, viscosity parameters and stress tests were also performed.
The workshop and in-studio material testing highlighted that the hydrogels can be used on a wide range of historical artworks such as paintings, mural paintings, paperwork, wooden objects, plaster, stone surfaces, metalwork, and contemporary modern materials. Depending on the nature of the material, whether polysaccharide, protein or synthetic, each gel shows slightly different properties in terms of transparency, purity, preparation methodology and viscosity to reduce solvent evaporation, optimise solvent action on the surface, improve moisture retention and implement gradual action on a painted surface. Most of these hydrogels can be potentially used also for salt extraction on porous materials such as historical wall paintings, brickwork, stone surfaces and metal surfaces. Their relatively easy preparation, application, removal and disposal make them safe for conservators and the environment. The issue of potential residues on the surface can be managed by changing the material percentage, a double cooking cycle (agar-agar) as well as the use of lens tissue or Japanese papers as a sacrificial layer.
The opportunity to take part in the workshop has also helped me to connect with an international community of conservators who face similar issues to mine. Talking to them and sharing different methodologies has been priceless as these connections afford a continuous exchange of ideas and brainstorming, which are fundamental for a conservator to be up to date and to provide the best conservation practice.
Final appearance of hydrogels such as borax gel and a PVA-agar-borax mixture. Image credit: H Tanday, Delta Conservation.