Gel cleaning of transparent and glossy acrylic surfaces in Qatar

Stefani Kavda, Emma Richardson, Stavroula Golfomitsou
University College London, Doha, Qatar
University College London, England
University of Gothenburg, Sweden

Transparent and highly polished plastic objects draw their aesthetic value from their optical qualities of clarity, weightlessness and transmission/reflection of light. Minimalist artworks created by Robert Irwin, Helen Pashgian and De Wain Valentine are exemplar of such sculptures, where once pristine surfaces are damaged with scratches and chips, the works lose their aesthetic properties and phenomenological characteristics. These artworks’ artistic value depends on their condition, severely reliant on their conservation. Simple mechanical cleaning can introduce abrasions and in turn, decrease the light reflective properties by reducing gloss. Wet cleaning treatments affect surfaces both chemically and physically, causing swelling, dissolution, or extraction of components. All these types of damage are likely to reduce the appearance of artworks, and at the same time, render cleaning one of the most delicate and complex operations in conservation.
It is thus of outmost importance to investigate treatments that do not exacerbate the visual damage of these artworks, often made of polyester and poly (methyl methacrylate). When such treatments are not in place and irreversible damage is induced, the need for more aggressive solutions is raised, to maintain the works pristine appearance. In an attempt to reduce the need for polishing and sanding, which increase surface stress and inevitably remove original material, systematic research was undertaken to investigate cleaning of poly (methyl methacrylate) with the use of gels. Pemulen/triethanolamine and poly (vinyl alcohol) gels were found to be the most successful and safe – among gel systems tested – at removing dirt.
To test the validity of the experimental findings on model surfaces, these were applied on objects from the Msheireb Art Centre collection in Doha, Qatar. The late 20th century transparent, colorless poly (methyl methacrylate) artefacts selected, a shop sign and two decorative lamp shades, were heavily covered by loose dust that hindered the observation of scratches, material loss and other surface defects. Soiling caused surfaces to appear dark and yellow, while cracking was visible, particularly around screws and metallic supports. One of the lamp shades also bared self-adhesive transparent tapes. Doha is characterised by high levels of pollutants and particulates. Analysis of dust showed high levels of calcite-based sand coming from the desert, as well as construction sites, fibres and decomposed rubber coming primarily from tires. In addition, high levels of nitrogen oxides, ozone and sulphur dioxide were recorded.
This paper will discuss the gel cleaning of these transparent and highly glossy poly (methyl methacrylate) artefacts exposed to a desert environment and the cleaning effects on their optical properties. It will take into account the main risk of conventional swab cleaning of heavily soiled surfaces, that is the redistribution of dissolved dirt and debate the selection of gels for their potential to act like sponges, ensuring absorption of dust molecules, and to reduce the levels of mechanical friction induced by the continuous rolling of swabs with dust particulates. The paper will furthermore discuss compromises, such as the invasive polishing of pristine artworks, that are sometimes inevitably made in conservation as part of a negotiation process.