41st Annual Meeting – Research & Technical Studies, June 1, “Contemporary Conservation for Contemporary Materials” by Yvonne Shashoua

Attending a lecture by Yvonne Shashoua, Senior Researcher in the Department of Conservation at the National Museum of Denmark, was such a treat, since she is so well-known in the field of plastics conservation, and her session did not disappoint.  Her calm, precise, and very approachable speaking style was impressive as she covered a scientific discussion on her current research into cellulose acetate degradation and its interaction with gas absorbents.  Since she will be presenting her findings in upcoming journals, I will only briefly go over what I learned and what you missed at this Research & Technical Studies AIC session.
Shashoua began by reminding us that plastics comprise an increasing proportion of museum collections.  Since it is difficult to detect plastic degradation until it reaches an advanced stage, a preventative approach, by either removing the factors causing or accelerating degradation, is usually taken.   Gas absorbents (silica gel, activated charcoal, Zeolite 4A, and Corrosion Intercept) are frequently used in museum storage and display situations to create a microclimate by removing specific gases.  She discussed how these materials are used and how they absorb pollutants, which I found very interesting.
Focusing on cellulose acetate, Shashoua discussed the mechanism of degradation (and the breakdown by-product acetic acid) and how additives (plasticizers and fire retardants, which are weakly bonded within the matrix) migrate out ultimately ending in shrinkage.  She was curious why the degradation process even begins in a museum environment, which began her in-depth research project. Cellulose acetate, has been used since 1910, but by the 1960s could be found in many objects: imitation mother of pearl, cigarette filters, early Lego bricks,  movie film bases and rayon.  By conducting a systematic study on the adsorbents’  interaction with cellulose acetate, she has found some startling results.  The adsorbents in some cases did slow down the onset of autocatalysis, however some also adsorbed the plasticizer and/or flame inhibitor, resulting in damage.  Her results suggest that commonly used absorbents in museums are non-specific and ineffective for cellulose acetate and, by extrapolation, other plastics.  She did rate the adsorbents  on a sliding scale; so reading her more in-depth post-prints will be a good lesson and/or review for all of us.  All this is startling news!  An archival acid-free box might simply be the best defense.  Wow.  I cannot wait to read her in-depth post-prints and journal articles concerning this fascinating subject.