Plastics in Peril: Focus on Conservation of Polymeric Materials in Cultural Heritage was a free online conference held on 16–19 November 2020. Bringing together conservators, scientists, collection managers, and researchers, the conference merged two events scheduled for earlier in 2020 that were impacted by the COVID-19 pandemic: a conference in Edinburgh organised by the University of Cambridge Museums, and a workshop organised by Leibniz Association of Research Museums.
Focusing on current practical solutions to manage plastics degradation, the conference took advantage of the virtual setting to engage an international audience with both live and pre-recorded talks, question-and-answer sessions, group discussion rooms, message boards, and audience polls. The event provided a splendid opportunity for both formal and informal networking and knowledge sharing, gathering over 1000 registered attendees.
A number of Australian participants associated with the Australian Research Council (ARC) funded Linkage Project ‘A national framework for managing malignant plastics in museum collections’ (PolyMuse), either braved the time zone difference or attended later through the recorded sessions. We now report back on our main findings, divided into five sections:
- Storage and management solutions
- Identification techniques
- Condition terminology
- Sustainability and collaboration
Storage and Management Solutions – Karina Palmer
Several speakers presented on the management and storage of plastics in museum collections. Georgina Raynor and Susan Costello at the Harvard Art Museum described a major collection survey that led to the implementation of several new management strategies, including new light exposure recommendations and the development of standard storage enclosures for vulnerable polymers. Cellulose acetate (CA) and nitrate (CN) objects are being rehoused in boxes constructed of acid-free board to help absorb acidic vapours. Poly(vinyl chloride) (PVC) objects are being placed on hand-made Mylar® trays and inside Mylar® encapsulations at 13°C and 40% relative humidity, to slow the loss of plasticisers. An amazing example was provided of a PVC sheet that had been in such an enclosure for five years, during which the plasticiser pooling on the surface had re-absorbed into the object! Low oxygen enclosures made from Marvelseal® and Escal®, flushed with nitrogen or with the addition of AgelessTM oxygen scavengers, are being used to prolong the life of some rubber items. The presentation also offered interesting examples of treatment and preparation for the exhibition of two objects, one made from PVC and another from reconstituted cellulose (cellophane).
Various presentations and panel discussions spoke of the use of cold storage as a preservation solution for vulnerable polymers. Christina Elsässer, representing researchers at the Deutsches Museum, determined using analytical and imaging methods that cracks in CN objects are not exacerbated by cold storage. Her research examined how composite objects, different shaped objects, and objects of differing degradations reacted to different temperatures and relative humidities of cold storage. Further work will determine if different rates of change in these latter variables affect CN in different ways. Similarly, at the British Museum, Marei Hacke and Capucine Korenberg described subjecting mock CN-covered badges to seven freeze/thaw cycles, fully exposed without enclosures, after which no additional cracking of the plastic was detected. The speakers of the session ‘Today’s and tomorrow’s sorrows’—Storage and global warming were asked if the preservation benefit of cold storage outweighed its environmental costs, and there was universal agreement that it did. Paraphrasing Capucine Korenburg, if society can afford cold storage for food and air-conditioning in shopping malls, we should of course be able to preserve cultural heritage in this way!
Valerie Tomlinson and Ruby Satele spoke about their ambitious plans for creating large-scale nitrogen-flushed anoxic enclosures for the storage of plastic objects within cold storage rooms at the Auckland War Memorial Museum. Artur Neves of the collaborative NEMOSINE project detailed the development of smart storage enclosures for CN and CA items that have built-in acid and moisture adsorbers, oxygen and carbon dioxide barriers, and gas detection sensors to monitor acetic acid and nitrogen oxide in real-time!
Other talks of interest came from Peter Giere of the Museum für Naturkunde in Berlin, who detailed the many hidden places one can find plastics in natural history collections, including plastic supports used for insect genitalia, polyurethane (PUR) foam supports inside taxidermied specimens, and fossil casts created from PUR elastomers. He mentioned the problem of distorted polyethylene (PE) drums housing wet collections when stored at low temperatures (around 14–16°C). Alice Cannon of Museums Victoria described her quest to find management frameworks for a huge and diverse collection where plastics lurk in many unknown locations. Those interested in collection risk assessments as they relate to plastics will enjoy watching Sue Warren’s discussion of this process undertaken at two major Canadian museums.
Treatments – Melanie Barrett
A number of the presented papers focused on the treatment of clear plastics—poly(methyl methacrylate) (PMMA), unsaturated polyester and polyolefin plastic sheeting. Joy Bloser, assistant conservator at the Museum of Fine Arts Boston, discussed the treatment of artworks made from plastic bags. Joy presented preventive methods to protect deteriorated sheet plastics on display, including using an isolating layer of Dartek® (nylon film) to protect aged and brittle plastics from mechanical damage, using Japanese paper bridges to structurally support brittle plastic forms, and using rare earth magnetic tape for mounting. As an interventive approach, Joy described manipulating low heat with variable temperature, pressure and time to re-join an assemblage of various delaminated plastic sheets. Identification of each plastic was essential to informing the heat settings of the treatment.
Ana Laganà from the Getty Conservation Institute highlighted the difficulty of treating transparent plastics with many treatments historically requiring the use of invasive methods, refabrication or deaccessioning. Ana’s research shows a clear alternative to these methods. For PMMA, RegalrezTM and HXTAL were used respectively to successfully repair scratches and chips. 3D scanning was presented as a method of casting infills for chipped unsaturated polyester resin objects, with the 3D printed material used to produce negatives in silicone which were then cast using epoxy and adhered to the object. Her paper shows the importance of matching the refractive index of infills to the polymer while keeping in mind the ‘compromise’ of stability versus aesthetic properties.
Stefanie Kavda, a postdoctoral scholar from the Deutches Museum, presented a case study of successfully cleaning PMMA objects using gels. Trialling PemulenTM/triethanolamine and poly(vinyl acetate) (PVAc)/borax gels, she determined that PemulenTM gels with water worked well for surface dirt, while the addition of a non-polar petroleum ether created an emulsion that was effective for removing adhesive residues. Risks identified included clearance issues and the expulsion of liquid from the PemulenTM, which may eventuate in crazing. Stefanie has published further scientific studies on various gel cleaning methods for PMMA.
Identification Techniques – Petronella Nel
The keynote by Petronella Nel and the session ‘What am I?’—Identification of plastics illustrated the ongoing search for methods to identify polymers in plastics. There was agreement across several presentations that polymer identification is a critical step, in conjunction with condition assessments, to inform preservation plans regarding storage and treatment. Out of this arose two main polymer identification research directions:
Non-Instrumental Decision Tools
Non-instrumental decision tools for identification were best exemplified by the Plastic Identification Tool, developed by Project Plastic and presented by Carien van Aubel and Lydia Beerkens. This project created identification boxes with reference materials and held two-day workshops at museums and galleries, followed by surveys of workshop participant collections. Outcomes of the workshops include training 111 people, surveying 10 collections and 825 plastics, and identifying 28 plastic types. The most common plastics identified were PVC, PMMA, PE, PUR, PS, and UP, with 20 per cent composed of malignant plastics. Sue Warren from Canada also conducted collection surveys where plastics were identified based on observation and experience. However, Sophie Rowe found via a precursor project that this type of decision tree is only 60 per cent accurate due to its subjective nature and highlighted the need for conservators to have relevant background experience.
Analytical Instrumentation Tools
For analytical instrumentation tools, Sophie Rowe exemplified the application of Fourier-transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) or external reflectance, stating these to be the current reliable gold standard used by research scientists. However, it was noted that FTIR is not easily used by non-specialists. Rowe concluded that near-infrared (NIR), used to sort plastics at recycling plants, and principal component analysis (PCA) may be the way to go. Conservator Susan Costello and scientist Georgina Rayner at the Harvard Art Museums demonstrated collaboration between conservators and scientists, applying FTIR and pyrolysis-gas chromatography–mass spectrometry (Py-GC-MS) for collection surveys, where the 12 most common types of plastics identified were: CN, CA, PVC, PU, rubber, PE, PP, PS, PET, PMMA, nylon and regenerated cellulose.
The session ‘From pop to blob’—Science driven decisions in plastics conservation further explored the use of scientific techniques to identify polymers in various heritage contexts. Julia Sawitzki used FTIR analysis to identify the different components in two robots at the Deutsches Museum in Munich. As part of a visual analysis of damage phenomena database project, Till Krieg, Cristian Mazzon and Elena Gómez-Sánchez used FTIR to survey 83 objects with 410 plastic parts. Results identified 36 different plastics, of which 91 were malignant and 10 per cent in poor condition. Francesca Modugno from the University of Pisa identified urban artists’ materials using various spectroscopy techniques to predominantly characterise synthetic polymers (alkyd, polyester, acrylic and PVAc), organic pigments and other additives. Notably, she identified the red paint in Keith Haring’s 1985 Melbourne Collingwood mural to be alkyd.
Condition Terminology – Katrina Watson
From discussions held during the conference around surveying collections, it appears that identification remains one the most difficult aspects of the management of plastics for many organisations. In the absence of advanced analytical instruments, such as FTIR spectroscopy, which is more commonly found in well-funded organisations and research institutions, many conservators in the discussions voiced concern that they felt like they were just guessing when it came to the identification of plastics. One method employed to aid identification is the use of established patterns of damage phenomena that can occur in plastics. In assessing and naming damage, and more specifically types of degradation, it is vital that the terminology is well-defined to be consistent and understood by others. Additionally, for conservation to move towards creating big data that can be used by the discipline at large, condition data need to be collected using linked concepts and common terminology.
In the session entitled ‘From pop to blob’—Science driven decisions in plastics conservation, a group of researchers from the Deutsches Bergbau-Museum [German Mining Museum] presented their research, which aims to take steps towards resolving issues related to condition terminology. While originally aiming to undertake a collection survey, the researchers from the Deutsches Bergbau-Museum represented by Till Krieg, Cristian Mazzon and Elena Gómez-Sánchez, ended up creating a visual atlas of plastics damage. In creating their database, as in the research undertaken for the ARC-funded PolyMuse project, they found that current condition terminologies either lacked definitions altogether, had inconsistencies, or had definitions that relied on casual explanations rather than observed phenomena. Through the processes of defining and refining, they developed hierarchical terminologies that cover six different damage categories: deposits, chromaticity/transparency changes, deformations, loss of integrity issues, identifiable smells and other/miscellaneous issues such as biological attack. We look forward to their future publications and possible collaborations with the terminology project being undertaken by the Technische Hochschule Köln [Technical University of Cologne].
Sustainability and Collaboration – Cancy Chu
Throughout the conference there was an underlying theme of sustainability concerning both the plastic materials that are so ubiquitous in both collections and the wider world, and the energy required to sustain practices for conserving plastics. This theme was highlighted by the keynote presented by Jill Sterrett, which described the process of designing a site-specific passive store that significantly decreased energy consumption at the San Francisco Museum of Modern Art. Strategies included taking advantage of the planned construction of a new storage site, collaborating between the curators, conservators and architects, and the formulation of a collection store access pattern that minimised human activity and therefore electricity use. Sterrett discussed the collective responsibility of society to save plastics heritage, emphasising the community contextualisation and creativity that was needed to best conserve cultural materials.
Several papers exploring low-cost monitoring, storage and identification methods were presented to provide solutions accessible to a greater number of collections. Mary Coughlin demonstrated the potential for ozone test strips to monitor poly(vinyl chloride) (PVC) degradation through experiments conducted at the Smithsonian’s Museum Conservation Institute and George Washington University. Valerie Tomlinson and Ruby Satele of the Auckland War Memorial Museum adapted industrial wine-making equipment for the creation of an anoxic environment in collection stores. Several talks described the development of non-invasive techniques for plastics identification in settings without access to analytical instrumentation, as previously mentioned under ‘Identification techniques’. The Plastic Identification Tool presented by Carien van Aubel and Lydia Beerkens from Project Plastics leads users to the most likely identification of a polymer based on observations of visual and physical characteristics.
Two papers additionally explored treatment techniques using green solvents. Angelica Bartoletti and Joana Lia Ferreira of the NOVA School of Science and Technology presented research on the use of supercritical carbon dioxide for cleaning and consolidating foams. John Morrison described the results of an experimental comparison of several green solvents used in paintings conservation for cleaning plasticised PVC at the University of Melbourne.
Participants were highly receptive to practical solutions that could be carried out with limited funding. Discussions around problem-solving with sustainable practices carried on in various chat rooms throughout the conference. As previously mentioned under ‘Storage and collection management’, speakers also discussed the cultural value of plastics justifying the reasonable use of resources for conservation work.
As an extension of the theme of sustainability, the acceptance and management of the loss of plastic collections was brought up by several speakers. Alice Cannon described the ongoing development of a plastics management strategy at Museums Victoria that draws on a number of existing strategies from other disciplines, including the practice of sentencing used in archives to deaccession collections after a pre-determined period. Gates Sofer and Joyce Townsend from Tate presented their research on the documentation of degrading CN and CA Naum Gabo sculptures with 3D laser scanning and photogrammetry, to enable the making of display replicas. The original sculptures are now stored using low-cost preventive techniques such as boxing and ventilation, with no further interventions being taken to restore the objects to their original condition. During the panel discussion ‘A blessing and a curse’—Plastic collections in the modern world, moderated by Katherine Curran of University College London, Mary Coughlin suggested maximising the access and display time of an object while it was in good condition, rather than prolonging the usability of the material beyond its natural timeframe with unsustainable practices. Speakers and panellists all highlighted the need to realistically re-evaluate conventional approaches and attitudes towards the collection and care of plastic materials.
Perhaps the strongest theme arising from the conference was collaboration. Many papers presented were the result of extensive cross-institutional work, such as the previously mentioned Plastic Identification Tool, the plastics identification surveys in Belgian museums presented by Hannah Hendrickx and Eline van der Velde, and the risk assessment surveys in Canadian museums presented by Sue Warren. Thea van Oosten highlighted the benefits of cross-disciplinary collaboration in her keynote Working side-by-side: The necessarily close collaboration between conservation scientist(s) and conservator(s) at restoration treatments. Case studies described by van Oosten additionally illustrated the benefits of collaborating directly with artists in the formation of display and preservation strategies. Similarly, Stefan Simon, a panellist on the previously mentioned discussion panel, emphasised the importance of cross-disciplinary communication within institutions, such that plastic objects were acquired by decision-makers with an understanding of limited usable timeframes.
As a researcher, I was particularly encouraged by the spontaneous formation of a message board for early career researchers in plastics heritage, initiated by Maria Lörzel of the Dresden Academy of Fine Arts after conversations in the PhD student chat room. Overall, there was a strong sense of community and desire for exchange that could be seen from active participant engagement throughout the conference.
As the last day drew to a close, participants filled in a live poll asking the question ‘What’s next for our community?’ The number one answer was: further collaboration.
As of May 2021, video recordings of the presented papers are available to the public through a YouTube playlist. Abstracts can be found through the conference website.