Conservation of Plastics: Materials Science, Degradation and Preservation

  • Yvonne Shashoua
Butterworth–Heinemann: 2008. 300 pp. $87.95, £49.99 9780750664950 | ISBN: 978-0-7506-6495-0

Many modern cultural artefacts, from Neil Armstrong's space suit to works of art, contain plastics that may degrade readily. Museums now face the challenge of saving vulnerable and important examples for future generations. Yvonne Shashoua's book Conservation of Plastics is a timely, thoughtful and thorough review of the young discipline of plastics conservation. It will help conservators, curators, archivists and collectors of modern materials, and will be of interest to materials scientists and chemists.

Often misidentified by the untrained eye, plastics are present in scientific, technological and social historical collections, and increasingly in modern art and textiles. Certain twentieth-century plastics, notably early polyvinyl chloride and polyurethane foams, degrade relatively swiftly and severely. Casualties include design icons such as the inflatable 1960s Blow Chair and highly collectable vintage Barbie dolls.

Semisynthetic plastics from the nineteenth century, especially cellulose nitrate (celluloid) and cellulose acetate, are particularly susceptible to degradation, whether the stimulus is physical, chemical or environmental. Irreversible damage to early celluloid cine film and its replacement, cellulose acetate safety film, pose a great problem for archivists. The earliest films and the historical evidence they contain may be lost unless they are transferred onto more robust media. The twentieth-century sculptor Naum Gabo used cellulose nitrate and cellulose acetate in his early works. Some have deteriorated so badly that conservators are turning to computer-aided methods to record their form.

Early steps to save plastics were discussed at a 1988 conference held by the Scottish Society for Conservation and Restoration. Several books followed. The 1993 Canadian Conservation Institute publication Saving the Twentieth Century, edited by David Grattan, established the discipline of plastics conservation. In their 1999 book Plastics: Collecting and Conserving, Anita Quye and Colin Williamson issued guidelines for the care of plastics in collections to acceptable museum and conservation standards.

A decade on, Shashoua's welcome and accessible book provides up-to-date, professional advice on caring for plastics, including associated risks and useful data. She provides context with introductory chapters on plastics in collections and the technology of plastics and their historical development, and uses her background as a polymer chemist and conservator to explain the nature of plastics, their types and related chemistry. Especially helpful are tables of frequently used additives, properties of plastics and the impact of chemical reactions in plastics, notably those caused by light, heat and oxygen.

To assist with the difficulty of identifying plastics, the book lists characteristic odours, recycling symbols and specific gravities. Shashoua discusses identification tests, including the controversial 'hot pin test', in which glowing hot pins are applied to the surface of a plastic object and note taken of the resulting marks and odours. This method is favoured by collectors and antique sellers, but rejected by museum professionals owing to the damage that can be incurred. She summarizes analytical techniques, including Fourier transform infrared and Raman spectroscopy, and supplies technical data that are useful to analytical chemists.

Shashoua includes dramatic case studies, such as the polyethylene head that was used to display a gas mask with vulcanized rubber strips. These had reacted chemically with the polyethylene so that the plastic head suffered irreversible and disfiguring degradation. This shows that sulphur-containing vulcanizing agents diffused from the gas mask into the polyethylene, and highlights the importance of using inert materials as display mounts for plastics.

Shashoua outlines available treatments, pitfalls associated with using solvents and the risks of cleaning and labelling plastics. She focuses on objects rather than media such as film, which is a specialization in itself. She highlights a need for better training for plastics curators, collectors and conservators, and outlines a strategy for surveying collections of plastics for degradation.

Global plastics production is rapidly increasing — around 230 million tonnes were produced in 2007. The compositions of emerging specialist plastics, such as composites, copolymers and blends, will make them even more difficult to identify and conserve and will challenge future collectors. With limited museum resources available, the future of plastics conservation will be subject to strict cost-benefit analysis. Saving Armstrong's space suit, for example, may warrant more expenditure than rescuing everyday, mass-produced plastic goods.

The book also touches on the conflicts between traditional conservation ethics and their application to new, short-lived materials, such as the biodegradable plastics being developed to offset mounting concerns about waste in landfills, landscapes and oceans. Biodegradable plastics provide increasing challenges to conservators as different types are being produced for an ever wider range of applications, from packaging to mobile phone casings.

The conservation of plastics is maturing as a discipline, but challenges lie ahead. Shashoua's guidelines in Conservation of Plastics do not supply all the answers, but they ensure the best chance of survival for current and future plastics collections into the twenty-second century.