Plastics preservation at the V&A

Brenda Keneghan
Polymer Scientist

Two previous articles on the subject of plastics degradation have appeared in the Conservation Journal since its inception. The first (issue 6, January 1993) was written by Edward Then, the original post-holder of the newly-founded position of plastics conservator, and Victoria Oakley, Head of the Ceramics Conservation Studio where the position was located. The piece outlined the strategy that was to be taken in tackling this recently recognised problem, beginning with a survey. In issue 21 (October 1996) a second article on the subject appeared under my name. The survey was almost complete and five polymers had been identified as those most susceptible to degradation. But by this time the problem had been recognised as more scientific in nature than previously thought, and the position was now located in the science laboratory. In 1998 the job title was changed to polymer scientist in recognition of the fact that the problem was chemical in nature and required a scientific background to understand what was happening before any approach to treatment could be even considered.

So what have been the main developments in plastics degradation and conservation at the V&A since that last article? As we delved further into the chemistries of the various materials involved several issues emerged. It became quite clear that plastics behaved differently and, therefore, must be approached differently to the more traditional materials. The main issues can be summarised as follows: There are very many different types of plastic - not just one. Of these many types, the results of our survey have shown that five1 are particularly susceptible to degradation and some actually cause damage to other materials while undergoing degradation. Each of those five plastics has a specific chemical composition and each must be treated as an individual material. Secondly, plastic materials generally degrade in a more dramatic fashion than the more traditional materials. This is because the deterioration of plastics has a relatively long induction period followed by accelerating degradation. In lay persons terms - what looks in fine shape one day may be a pile of dust six months later. Thirdly, what may appear a relatively innocent treatment, e.g. swabbing a surface with solvent or adhering broken parts, may result in much more severe damage appearing at a later date. Finally, it must be accepted that the degradation of plastics is due to irreversible chemical reactions. Although it cannot be reversed it can, given the right conditions, be slowed down.

Armed with this information a more holistic approach to the problem has evolved and the focus has shifted slightly from conservation towards preservation. Raising an awareness of the problem and education were the first steps taken in tackling the deterioration of plastic objects in museums. To this end, the results of the survey have been the topic of several departmental seminars, conference presentations and invited lectures, as well as forming part of the annual lecture on the subject to students on the RCA/V&A Conservation programme. They have also been published in the journal 'Museum Management and Curatorship', in the hope of reaching the widest possible target audience, as it is curators who generally come across the objects in the first instance, especially in the smaller museums. At least by being aware of the possibility that some plastic objects in their collections may be degrading, museum professionals can keep their eyes (and noses!) open for tell-tale signs and smells.

On the educational theme, plastic identification workshops for conservators and other interested parties were planned. Before taking them into the studios, however, trials of the published chemical spot tests for identifying various plastics were undertaken in the laboratory. These tests were found to have serious drawbacks which make them unsuitable for use by the conservator in the studio. As well as requiring toxic chemicals, many of the results are subjective. Most of the tests only appear to work when the identity of the material is already indicated in some other way. Testing completely unknown samples showed the results to be highly ambiguous. However, as in reality most historic plastic materials are reasonably stable, it is really only the five highlighted ones (especially in older objects) that need to be identified in collections. The two most dangerous materials with respect to the damage they may cause other objects, are cellulose nitrate and cellulose acetate. These plastics are no longer in general use and mostly their occurrence relates to reasonably specific time periods and the imitation of natural materials. It is therefore possible to approach their identification in other ways, e.g. by the style of objects or by their date etc., and also by keeping an eye on any suspect objects. Unfortunately newer objects made from synthetic polymers can also cause problems, as artists especially often use these materials for the novel effects that can be produced without paying due care to the manufacturers instructions. Thus the resulting stability problems, in contrast to the historic objects, are often avoidable.

Figure 1

Figure 1: Modern plastic furniture from the V&A collection. Photography by Nigel Bamforth (click image for larger version)

Although we do not have all the answers yet, we are now pretty clear on what the problems are, and the next stage in our strategy is to investigate the long-term effects of recommended conservation treatments on selected degraded plastic objects. While we are approaching interventive treatments cautiously, minimal cleaning is currently undertaken for some objects, most recently on several pieces of pop furniture from the 1960s and 70s (Figure 1).

Continuing with the preservation course, control of the environment is essential to help prevent or slow down the degradation reactions of polymers. Therefore, the correct choice of storage conditions is vital for the preservation of plastics especially the five most susceptible polymers. A current project in this area is the assessment of the best storage environment for photographic negatives. The Museum has large photographic archives which contain negatives with bases made from both cellulose nitrate and cellulose acetate. The negatives are degrading rapidly and we are in the process of evaluating the various packaging systems before placing them in cold storage. As commercial packaging systems are extremely expensive and often contain non-essential elements, a knowledge of the different degradation chemistries involved allows the most cost-effective system to be chosen.

The formation of the Contemporary Team and the dedication of gallery space to the 'Contemporary' has resulted in very successful exhibitions of non-traditional content. These have included Brand.New, Zoomorphic and Brilliant where plastics were in abundance. 'Touch Me' actually invites the public to do just that to objects, many of them made from synthetic polymers. In response to the changing nature of the objects being accessioned and also these different types of exhibitions, curators now regularly ask for information about synthetic plastic objects before making decisions on their accession or inclusion in an exhibition. As we publish issue 50 of the Conservation Journal I can honestly say that the "plastics denial syndrome" which was particularly prevalent in the various collections, and referred to in issue 211 , has been eliminated completely.

As the subject of plastics degradation has become more widely publicised, interest continues to come from national and international radio, newspapers and art magazines. As more and more art objects are made from these relatively unstable materials, the problem is likely to increase. The Conservation Department at the V&A remains a leader in the field tackling this problem and is regularly contacted for advice and assistance by a wide range of organisations ranging from regional museums and other heritage bodies to auction houses.

References

1. Keneghan, Brenda., 'Plastics? - Not in my collection, 'V&A Conservation Journal No.21' (October 1996), pp.4-6