By Bertrand Lavédrine, Rachel Rivenc, and Michael Schilling
Following their introduction at the end of the nineteenth century and their rapid proliferation since the 1950s, plastics have touched every facet of modern life. Their extraordinary versatility, together with the possibilities they offer for experimentation, have made them very attractive materials for designers, architects, and artists. Objects made wholly or in part from plastic form a significant area of modern and contemporary cultural heritage, including Enrica Borghi's Vestito Blu (2005), a spectacular piece made from bottles of mineral water and plastic bags.
Unfortunately, many plastics deteriorate rapidly due to irreversible chemical reactions, leading to a number of dramatic physical changes: discoloration, opacification, loss of gloss, crazing, cracking, warping, sagging, becoming sticky, crumbling, and powdering. Antoine Pevsner's Portrait of Marcel Duchamp (cellulose nitrate on copper with iron), for example, shows many of these forms of degradation. Interestingly, many of the plastic objects that exhibit more pronounced deterioration are made from just four specific classes: cellulose nitrate, cellulose acetate (both of which are probably present in the Pevsner piece), polyvinyl chloride (PVC), and polyurethane. However, other classes may also become problematic with time; even objects that appear to be in pristine condition and exhibit no visible signs of damage may still be at risk. This is because some mechanisms of plastic deterioration have been shown to include relatively long induction periods during which they appear largely unchanged, followed by rapid deterioration. Experienced conservators of plastic objects know all too well that appearances can, indeed, be deceiving.
Knowledge about the composition and aging of synthetic polymers—of paramount importance to curators and conservators entrusted with the care of plastic objects—is often not readily accessible. Despite some excellent individual studies into these issues, there is scant collective experience in dealing with these objects, few insights into the nature and use of modern materials in artworks, and no generally accepted criteria and methods for solving the conservation problems they pose. Thus, there is an urgent need for obtaining and disseminating information on the material composition, physical and chemical properties, and aging behavior of a range of plastics—information crucial for devising strategies to slow deterioration rates and for assessing treatment options and their potential long-term impact on plastic objects.
A RESEARCH CONSORTIUM
In recognition of these significant needs, the Getty Conservation Institute has joined a consortium of European institutions and laboratories, all of which are involved in the care or study of modern and synthetic materials, to develop and execute a three-year European Commission-funded project entitled Preservation of Plastic Artefacts in Museum Collections (POPART). Coordination and management of the project are orchestrated by the Centre national de la recherche scientifique (CNRS) through the Centre de recherche sur la conservation des collections (CRCC) in Paris. Other partners include the Centre de recherche et de restauration des musées de France, the Victoria and Albert Museum (United Kingdom), the Istituto di Fisica Applicata "Nello Carrara" (Italy), the Instituut Collectie Nederland (Netherlands), the Polymer Institute of the Slovak Academy of Sciences (Slovakia), Arc-Nucléart (France), SolMateS BV (Netherlands), Morana RTD (Slovenia), University College London (United Kingdom), and the National Museum of Denmark.
The main objectives of POPART are to identify the principal risks associated with the exhibition, cleaning, protection, and storage of plastic artifacts, and subsequently to develop a strategy to improve the preservation and maintenance of three-dimensional plastic objects in museum collections. More specifically, the POPART project focuses on four key research areas:
Analysis of Plastics
Identifying the type of material from which an object is made is often a prerequisite to decisions about its conservation. This step is critical for plastic objects because synthetic polymers exhibit such widely different stabilities and deterioration patterns. A particular conservation intervention might be appropriate for one type of polymer but have disastrous consequences for another.
One of the main objectives of POPART is to develop and evaluate a range of analytical tools and methodologies for identifying as many classes of plastics as possible, initially with a set of one hundred reference samples assembled for the POPART project and circulated to each partner institution. Priority will be given to noninvasive analytical techniques (those that do not require sampling), such as near infrared spectrometry (NIR), Raman spectrometry, and Fourier-transform infrared spectrometry (FTIR), and especially to those techniques that offer handheld portable devices, as these open up the possibilities of rapid, on-site surveys of large collections. Minimally invasive techniques, which require the smallest of samples, such as pyrolysisgas chromatography/mass spectrometry (Py-GC/MS), will also be included because of the high level of detail they can provide on the chemical composition of the sample. The GCI is coordinating an interlaboratory round-robin evaluation of data reproducibility and efficiency of the different methods for characterizing plastics. One practical outcome of this study will be a collection of analytical databases shared by the research partners.
Collection Surveys and Condition Monitoring
in Museum Collections
Another important objective will be the identification and documentation of typical deterioration patterns in plastic objects—such as discoloration, change in opacity, crazing, cracking, changes to surface texture, and distortion. Documentation methods and condition reporting tools currently used for surveying collections will be compared and combined to create a single survey form. This will be used to survey a number of plastic collections in museums, including the Victoria and Albert Museum in London and the Museum of Modern and Contemporary Art in Nice. The aim is to document deterioration systematically and consistently, thereby allowing more direct comparison between the collections surveyed. Noninvasive spectroscopic characterization of the polymers in objects will also be performed as part of this process, and the focus will then turn to monitoring volatile products off-gassed by a group of selected objects and analyzing materials deposited on their surfaces.
Assessing Polymer Degradation
Studies into the degradation mechanisms of plastics and their ramifications generally require longer periods of investigation than the three-year timetable of the POPART project. However, some classes of plastics are far more problematic than others (i.e., cellulose plastics, PVC, and polyurethane) and require immediate attention. Degradation pathways for the two cellulose plastics have previously been investigated by those responsible for the conservation of early motion picture film. It is unclear, however, how much of this information can be applied to the study of three-dimensional objects, given the differences in composition between cinematic film and bulk polymer. In the case of PVC and polyurethane, a great deal of research is still needed on the influences of humidity, temperature, and oxygen on deterioration rates. Off-gassed volatile compounds will be studied in order to assess risks to museum collections as well as to museum staff. The GCI will apply several thermal analysis techniques to monitor polymer degradation and to track changes in the mechanical and thermal properties of polymers with aging.
Evaluation of Conservation Treatments
One of the most complicated areas in conservation is the assessment of treatments, yet this is a primary concern for conservators. The POPART project felt it was important to include an aspect of conservation treatment within the scope of the project, and it was decided to concentrate on two very different treatments: cleaning and consolidation. As with all works of art, plastic objects eventually require surface cleaning, but very little is known about the effects of various cleaning materials on plastics, apart from the fact that many organic solvents can dissolve plastics. A systematic study on a small subset of plastics will therefore be executed to study various cleaning methods and to assess their potential for damage on those polymers. Highly experimental methods of consolidation will also be assessed for very fragile and deteriorated artifacts—in particular the use of in situ gamma ray polymerization.
One of the most important aspects of POPART will be the dissemination of research results to other conservation professionals. This will happen periodically throughout the duration of the project, through journal articles and conferences as the primary mechanisms, and through regular updates at the project Web site.
The POPART project, which constitutes a major part of the GCI's research into the preservation of plastics, will involve six Institute scientists: Michel Bouchard, Herant Khanjian, Tom Learner, Alan Phenix, Rachel Rivenc, and Michael Schilling, as well as GCI Postdoctoral Fellow Emma Richardson.
In addition to POPART, the GCI has initiated a close collaboration with the Getty Research Institute to investigate various plastics and resins used by Finish Fetish artists of 1960s Los Angeles, whose work will be featured in the exhibition Pacific Standard Time: Art in Los Angeles 19451980, to be held at the J. Paul Getty Museum in 2011. The GCI is also collaborating with a number of other institutions on plastics research, including the Los Angeles County Museum of Art, Yale University Art Gallery, the Smithsonian Museum Conservation Institute, and the Disney Animation Research Library.
Bertrand Lavédrine is director of the Centre de recherche sur la conservation des collections (CRCC), Paris. Rachel Rivenc is a GCI research lab associate. Michael Schilling is a GCI senior scientist.