To many of us, Corian is familiar from interior fittings in kitchens and bathrooms. Since its development in 1967, Corian has been applied by architects, designers and artists. Due it its durability and its widely inert behaviour, it is also used for display cases and pedestals. Thus, it is not surprising that the conservation treatment of an artefact made of Corian has hardly been an issue for conservators to date. Corian® is DuPont’s brand name for an imporous cast stone made of one third acrylic resin (polymethylmethacrylat, PMMA) and two thirds aluminium trihydroxid, a mineral extracted from the aluminium ore bauxite.
The white material can be pigmented and patterned by adding shredded Corian beads. The boards of mostly 6 or 12mm thickness can be worked with woodworking tools, but also heated and thermoformed. For obtaining seamless surfaces, a separate Corian glue is provided, which contains not only PMMA and the inorganic filler but also the monomer methyl methacrylate (MMA), serving as reactive solvent.
The seams are generally the weak points of the otherwise robust material: low polymer density along the joint reduces mechanical stability and increases transparency of the material. Friction of the aluminium edge guide of a circular saw can cause gray staining; the binding medium of some sanding papers can leave yellow friction wear. If not fully removed, it will stain the adhered joints.
The series “Shapes” made in 2006 by the American artist Allan McCollum consists of blocks of slightly translucent Corian plates, which are sandwiched to a depth of 17 cm. Their pliant contours resemble vaguely abstract animals and the smooth surface evokes the impression of pristine white marble.
After the initial exhibition, grey and yellow staining became visible along some of the joints and others were filled incompletely with glue so small grooves opened up. Since these manufacturing marks contradict the idea of the perfect material, the artist prohibited further exhibition or sale in the current condition. Due to the very high material and manufacturing costs and the risk that the same problems will occur again, the remake of the sculptures is not an option and a method for local restoration needs to be found. Even extreme solutions, such as sand blasting and over-painting, are approved by the artist.
In order to learn how Corian sinks and worktops are professionally repaired, a workshop at the DuPont training centre was attended. It became clear that the only way to remove the stains is to cut them out, and to put in inlays. The hardness of the material requires heavy-duty machines with an edge guide. Given the organic silhouette of the “Shapes”, this is hardly possible. Moreover, small enough milling heads suitable for machining hard wood are not readily available, nor are cutting heads for the preparation of precise inlays. Filling the grooves with Corian glue is also problematic due to the changes in transparency. An optically satisfying and efficient solution has not been found yet, but more options will be tested.