Agar Bioplastic:
Understanding Its Degradation
and Exploring Its Use as a Fill For Glass
During the second year of graduate study at WUDPAC, students undertake a year long research project applying analytical chemistry techniques learned in their science courses. My second year research project examined the degradation and stability of agar bioplastic, and the potential viability of agar as a fill material for conservation of glass objects. I presented my findings at The Association of North American Graduate Programs in Conservation (ANAGPIC) 2022 annual conference. This research project was supplemented with a semester-long independent study course examining and experimenting with fill materials for glass conservation. See Research tab for more information on the findings of that course.
Though most commonly used as a thickening agent in foods and a solidifying component of bacteriological culture media, agar has been widely accepted as a rigid gel used across conservation disciplines. While many studies have shown its suitability and efficacy as a cleaning material, agar is often seen as temporary, not something where longevity is needed or desired.
Art made of bioplastics (left Yi Hsuan Sung, agar) (right Erik Klarenbeek, Maartje Dro, algae)
In recent years, agar has been explored more widely as a bioplastic alternative to traditional plastics. Bioplastics, or bio-based plastics, are plastics made from natural, raw materials rather than petroleum products. Many art schools are pushing students to experiment with these new and unique materials, testing their limits. With art students learning about these materials, it only makes sense that more bioplastic artworks are entering museum collections and will soon come under the purview of conservation. Museums with design collections such as the Philadelphia Museum of Art, The Museum of Modern Art in New York and the Cooper-Hewitt Smithsonian Design Museum have all begun acquiring bioplastics and are coming face-to-face with the reality of how to care for these materials.
Inspired by artists working with agar to mimic glass, this study was designed to understand the degradation of agar bioplastic as an artist’s material but also for its potential viability as a fill material for glass. This study evaluates the stability of agar, and thus the potential stability of art and fills made from the material, by examining the long-term effects of a typical museum environment (controlling temperature and relative humidity) on two different purities of agar using accelerated aging and an array of analytical techniques. Artificially aged agar was analyzed using visual observation, thickness measurements, colorimetry, Fourier Transform Infrared Spectroscopy (FTIR) and Pyrolysis-Gas Chromatography-Mass Spectrometry (py-GC-MS) to understand its degradation and see if the physical and chemical changes it undergoes are detectable with analytical instrumentation.
Samples before (day 0) and after (day 21) accelerated aging.
Overlaid FTIR spectra of lab grade agar samples from days 0, 3, 7 and 21, showing no detectable chemical change.
Agar experienced significant physical changes upon aging which were detectable with and without various types of instrumentation. Building on the information learned from the aging study, the viability and application of agar as a fill material for the conservation of glass was explored through hands on experimentation and comparison with accepted conservation materials.
Agar fills on colored glass (left), clear glass at front (center) and clear glass at back (right)
When compared to traditional glass fill materials, agar acted and looked most similar to Paraloid B-72, a readily accepted and widely used fill material. Though by no means a perfect alternative to B-72 or glass-specific epoxies, agar could be a viable material option for temporary fills where longevity is not required. The notable changes in color and thickness of agar caused by aging would be problematic for artworks made of the material, as well as if it were to be used as a conservation material on objects. This project has shown that further research into alternative materials would be valuable for the field of art conservation.