A preliminary investigation into the influence of archaeological material on the yellowing of polyethylene storage bags

Abstract

Concerns around the degradation of plastics have been part of conservation discourse for decades. The spotlight is usually on art and objects, and conservation and display materials, however it could be argued that a significant volume of the plastics in museums is associated with storage bags. This study asked whether the condition of plastic storage bags might be influenced by what is stored inside them. If specific materials can be identified as more likely to affect plastic degradation, museums may have a lead-indicator for efficiently monitoring storage risks. This case study developed a methodology for applying multivariate analysis to collected data to answer this question. A subset of polyethylene self-seal bags used to pack archaeological material from the ‘Casselden Place’ assemblage at Museums Victoria was evaluated. Objective data were combined with subjective assessment of bag degradation features gathered during a collection survey and interrogated using multivariate statistical analysis. Results indicate (1) different levels of yellowing are associated with particular plastic bag stocks and (2) ceramic, slate and tile finds are more likely than other materials to be contained within yellower bags. The research points to future enquiry and demonstrates this methodology shows promise for extension to other large cultural datasets.

Keywords:

• Polyethylene
• yellowing
• storage
• archaeological finds
• preventive
• data-intensive methodologies

Acknowledgements

The authors would like to thank Museums Victoria for facilitating this research, particularly Alice Cannon. The authors also acknowledge the work of Museums Victoria’s Material Scientist Rosemary A. Goodall. This research is supported by the Australian Government through the Australian Research Council’s Linkage Projects funding scheme (LP160100160). Thanks also to Dr Sarah Hayes, Senior Research Fellow, Deakin University, for data from The Historical Archaeology of the Commonwealth Block 1850–1950 ARC Linkage project. And to Peter Grigaliunas, Director, Griga Actuarial Consulting, for statistical modelling advice.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research is supported by the Australian Government through the Australian Research Council’s Linkage Projects funding scheme [grant number LP160100160].

Notes on contributors

Karen M. Thompson

Karen M. Thompson is a Senior Research Data Specialist at the Melbourne Data Analytics Platform (MDAP) at the University of Melbourne. She has a BSc (1993) in Mathematics from the University of Queensland, was a Fellow of the Institute of Actuaries of Australia (2003-2021), has a Bachelor of Fine Arts (2006) in Gold and Silversmithing from Royal Institute of Technology in Melbourne, and a MA in Cultural Materials Conservation (2018) from the University of Melbourne.

Petronella Nel

Dr Petronella Nel is a Senior Lecturer at the Grimwade Centre. She has a BSc Honours (1990) in Chemistry and a PhD in Chemistry (2000) and MA in Cultural Materials Conservation (2006), from the University of Melbourne. She is currently leading an ARC Linkage Project ‘A National Framework for managing malignant plastics in Museum Collections’ in partnership with Museum Victoria, Queensland Museum, Museum of Applied Arts and Sciences – Powerhouse Museum, South Australian Museum, Australian National Maritime Museum, Art Gallery of NSW, University of Sydney, University of Technology Sydney and Flinders University.