Aqueous cleaning methods for hyperrealist silicone rubber sculptures

Laura Wolfkamp (UVA), Evelyne Snijders (UVA), Suzan de Groot (RCE)
Cultural Heritage Agency of the Netherlands (RCE) Amsterdam, The Netherlands
University of Amsterdam (UVA), The Netherlands

Silicone rubbers have been increasingly used by artists since the 1990s. They are found by themselves or in combination with other materials, and can be used as casting materials, negative molds, adhesives and even paint media. In particular, they are used in hyperrealist sculptures to create a lifelike imitation of human skin. Examples can be found in the work of Ron Mueck, Patricia Piccinini and Paul McCarthy, as well as the Dutch artists Margriet van Breevoort and Peter Zwaan.

Silicone rubber surfaces tend to attract a lot of dust and dirt, and this can be caused by several factors. One is their significant electrostatic charge, and their inability to discharge it due to their insulating properties. Another is their relatively low glass transition temperature, which makes it easy for dirt to adhere to the surface. Also the presence of exuded silicone oil on the surface may attract dust and dirt. Because soiling can accelerate degradation processes and attract biological growth, the removal of surface dirt is an important conservation measure. Besides, surface cleaning serves an aesthetic purpose. Although the current consensus among conservators is that aqueous methods are best used for cleaning silicone rubber artworks, the effect of surfactants on this material has not yet been thoroughly studied.

The paper presented here investigates the suitability of eight aqueous cleaning agents combined with two application methods for the removal of dirt from silicone rubber surfaces. Hyperrealist sculptures were chosen as a focus, because the perfect appearance of these artworks is important for maintaining the illusion of realism. Since soiling may consist of many different components, the focus is on the effect of these methods on the silicone rubber surface rather than their cleaning efficiency. A cleaning method is considered suitable if it does not induce changes to the surface; does not leave residues on the surface; and does not accelerate degradation processes in the material. These aspects were investigated by exposing silicone rubber samples to immersion experiments, cleaning experiments and artificial aging. They were evaluated through macro- and microscopic examination, as well as measurements of gloss, contact angle, and color.

It was found that the tested methods do not leave significant residues on the silicone rubber surface, and do not stimulate the degradation of the material. However, mechanical action should be kept to a minimum for many reasons, most importantly to avoid changes in gloss and removal of thin finishing layers. The surfactants Dehypon LS45 and Ecosurf EH-6 were found to have more affinity with silicone rubber than the other cleaning agents tested. Based on these findings, the paper presents a general approach for cleaning hyperrealist silicone rubber sculptures, which could possibly be transferred to other artworks made from silicone rubber.