A plethora of plastics is everywhere we look. The RISD Museum is continually acquiring art composed of polymers, colloquially referred to as plastic. What is not so obvious is that plastics have been in existence for well over a century and are incorporated in museum collections from the smallest historical society to our nation’s attic, the Smithsonian. Plastics were originally invented as substitutions for certain natural materials, and in many instances their manufacture addressed a specific industrial need, especially during times of war.
The earliest polymers include rubber and latex. Because these materials are derived from nature, they have a limited life span. Domestic articles and apparel of all types can be composed in part of these materials. Unfortunately, oxygen leads to the demise of objects made from rubber and latex. They have rather short life spans, and often require replacement parts.
Some of the first man-made plastics are cellulose nitrate and cellulose acetate. The earliest film for the motion picture industry was composed of cellulose nitrate, and cellulose acetate was used by Walt Disney for his animation cells. In the 1920s and ’30s, many of Constructivists, such as Naum Gabo and Laszlo Moholy-Nagy, were experimenting with these materials. Unfortunately, they decompose over time because of unstable internal chemical reactions. Early films made from cellulose nitrate are particularly dangerous, as this material can be explosive as it ages.
In the early 20th century, a synthetic plastic called Bakelite was invented. Ubiquitous in the jewelry industry of the 1920s, Bakelite is considered chemically stable. In the 1950s, other stable forms of plastics were introduced, including acrylics such as Plexiglas and polycarbonates such as Lexan, both of which can have an indefinitely long life when incorporated into a work of art. The invention of polyethylene (PE) and polypropylene (PP), both of which are quite stable, has allowed a wider variety of plastic materials that can be utilized, recycled, and “upcycled’ by contemporary artists.
Unfortunately, not all synthesized plastics are stable. The invention of plasticized polymers became more problematic, as plasticizers create a flexible but unstable plastic. To illustrate this point, compare the rigid PVC (polyvinylchloride) used to create vintage LP records with a more plasticized version of PVC such as that used to create some dolls including Barbie and Ken. The instability of a plastic can often be revealed by its chemical off-gassing, and can be readily apparent if it smells like a new shower curtain. In addition to their blatant chemical scent, plasticizers migrate throughout the polymer molecule structure and can create a sticky residue on the surface of the plastic art work over time. This phenomenon can be observed on early garment bags.
Another particularly unstable polymer that is somewhat ubiquitous is polyurethane foam, which is damaged by light and disintegrates over time. This material provides challenges from the preservation point of view. Since the 1940s, polyurethane foam has been used in all sorts of upholstered materials and other stuffed things. These foams, although initially resilient and compressible, become very rigid and crumbly over time. An artwork what was initially flexible in its construction and can become delicate and fragile over time. Another challenge for the museum conservator!
Art composed of plastics or polymers are challenging to preserve for any museum. Identification is the first line of defense. If the plastic can be identified, then a safe, long-range conservation plan can be proposed. Selecting art made from stable, as opposed to less stable, plastics is always an option and should be considered. Art composed of plastic must be exhibited at low light levels (five footcandles / 50 lux or less). Shorter three-month rotations for plastics considered less stable should be encouraged. Ambient dust accumulation is particularly detrimental to and difficult to remove from plastics which are flexible and contain a fair amount of plasticizers, as the dust will eventually bond and become difficult to remove. Considerations during storage include whether to ventilate the artwork or not, whether to reduce the oxygen levels to which the art object is exposed within the storage container, and whether or not to isolate the plastic material from other collection materials, such as metals, that are prone to corrosion from plastic off-gassing. If the artist is living, their long-term preservation preferences should be diligently sought out.