Treatment of an extruded polystyrene and cork wood sculpture

Huma Bhabha's Waiting for another game is a three-metre tall sculpture. The figure has four faces and the upper body is carved from adhered layers of pink, green and blue XPS. This section is decorated in a graffiti-like style with fluorescent paints and oil sticks. The lower body and legs are carved from charred corkwood.

The sculpture had areas of loss on the XPS face, neck and torso. The areas of loss were quite deep, which disfigured the overall appearance of the sculpture.

After consultation with the artist and National Gallery curators, it was decided that treatment was necessary because the losses around the face were too noticeable.

I contacted Huma Bhabha and she sent me a list of materials used to make the sculpture. Bhabha often uses found materials, so I undertook FTIR-ATR spectroscopy of the sites of loss and confirmed XPS for the polystyrene layers and PVA adhesive bonding the layers.

XPS is a polymeric material that can easily be dissolved with solvents, so appropriate testing was conducted to ensure adhesives, fills and paints would not disfigure the original materials. There were few example case studies of fills for XPS, so I had to experiment with conservation and commercial materials to find a solution.

The sculpture had to be treated upright and offsite in a storage corridor. Working from a ladder to reach the top of the three-metre sculpture meant there were limitations to the types of materials I could use that would enable me to work safely.

The texture of the sculpture is quite coarse and variegated, and so some of the areas  could be left without the need for filling or painting. It was too complex an undertaking to locate the original positions of all the XPS crumbs. After some tests I chose paper pulp as the fill material because it is lightweight like XPS, it can be textured to mimic the artist’s carving, and it is a conservation-grade material. A barrier layer of methyl cellulose was used, and the fill was a combination of paper pulp, methyl cellulose and deionised water. Toothpicks were used to texture the surface while the pulp was wet. I made a relatively dry pulp because the sites of loss were on a vertical plane and I had limited ways to prevent the fill from sliding while drying. A few layers were applied to account for shrinkage.

To differentiate from the materials used by the artist, I chose gouache paints as my inpainting medium because they matched the matte appearance of the original paints. I painted a base layer of colour that matched the XPS (pink, green or blue), then stippled layers of black, green, pink and white over these areas, according to reference photos. I managed to make a close match to fluorescent pink using gouache that was slightly dull, so I added an additional layer of fluorescent acrylic paint.

From a distance, the overall infills and painted surfaces blend well. Before and after images of the treatment were sent to the artist. She was very happy.

Since this was my first experiment with paper pulp fills in polystyrene, I learnt that it is important to allow enough drying time between layers of pulp to make sure there is not too much shrinkage, and to spend time making sure the base texture and background colour are consistent with the original materials. I hope to do ageing tests on samples of XPS and the fills and paints I used to predict changes to the fills over time.