In some cases, we want plastic to disintegrate and disappear, such as in bags, bottles, and cutlery. But when it comes to art, we want plastics to last forever. But as Senior Editor Sarah Everts reports in Chemical & Engineering News, plastics don’t last forever, and there is whole scientific craft now emerging to save plastic art.
Artists are always interested in using novel materials, like plastics, in their work. But they often don’t appreciate that, unlike stone or bronze, plastics have a limited lifetime.
Almost all plastics darken with time, as harsh light conditions transform their polymeric ingredients into yellow, orange, or brown molecules. Furthermore, light and temperature fluctuations combine with oxygen and water in the air to break apart the polymers that make up the plastic. The degradation products tend to leach, joining an exodus of plastic additives included in recipes to make the material malleable or to protect it from ultraviolet light or heat. As essential components exit the plastic pieces, artwork begins to crack and crumble — just as a plastic bottle does when left in the sun.
The use of plastics by artists has shot up since the 1960s. But it was only as recently as the 1990s that museum conservators realized that plastics don’t hold up forever and need to be saved.
Four classes of plastics are more prone to degradation than others: cellulose acetate, cellulose nitrate, polyvinyl chloride, and polyurethane foam. Because of the various chemistries involved with these plastics, museum conservators have to deal with each plastic on its own.
Everts introduces us to Thea van Oosten, a conservation scientist at the Cultural Heritage Agency of the Netherlands. Van OostenÂ uses a spray-on light stabilizer called Tinuvin to protect polyurethane from light damage and extend its life. But the problem is Tinuvin can turn some artworkâ€™s matte look to glossy, a change that’s unacceptable for a number of artists and curators.
But polyurethane is an oddball, given there is something available as a spray to save it. Most conservators try to save plastic objects by changing the surrounding environment. For cellulose acetate and cellulose nitrate, used as replacements for ivory and tortoise shell in jewelry and in early movie and photographic film, light, heat, and air breaks them down. They release nitric acid and acetic acid, which, if not removed, catalyze further degradation of plastics.
So far, the antidote to the damage from these acids has been adsorbents. These are activated carbon for nitric acid and zeolites for acetic acid, which conservators put near plastic artifacts to trap the acids. But conservators aren’t sure exactly how effective is this strategy.
As museum staff around the world increasingly realize that plastics in their collection are vulnerable, a growing amount of work is being done to find solutions to a problem that is unlikely to go away. For example, conservators from the Smithsonian Institution museums and galleries in the U.S. are trying to create a plastics working group to research and share solutions to plastic degradation problems. In Denmark, museum curators, conservators, the plastics industry, and artists are also starting to work together to fight plastic art degradation under a program called Plastics Research & Innovation for Museums & Industry.
Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.