Emily Brzezinski
Cellulose nitrate is notorious for its dramatic deterioration that leaves the plastic extensively crizzled and crazed, eventually leading to disintegration. The Smithsonian, National Air and Space Museum (NASM) holds innumerable cellulose nitrate objects, including a navigation board used by aviators Charles and Anne Lindbergh in the 1930s. The navigation board comprises a wooden backing board, steel hardware, and a transparent cellulose nitrate sheet protecting the paper charts. Inherent vice and poor storage conditions have caused extensive crazing and breaks to the cellulose nitrate, placing the plastic’s structure – and therefore the legibility of the entire object – at risk. Adhesive consolidation or facing was required to preserve the integrity of the original material.
While conservators have undertaken more interventive treatments of plastics in recent years, there is a paucity of publications concerning adhesives used in the treatment of cellulose nitrate objects. The study began by surveying conservators at NASM and the broader community, asking what adhesive methods conservators use to stabilize cellulose nitrate and how the treated objects fared over time. Informed by these results, several adhesives were tested in combination with deteriorated cellulose nitrate. The sensitivities of the plastic restricted experimentation to adhesives soluble in water, non-polar solvents, and emulsions. These adhesives were assessed for their efficacy in stabilizing breaks through facing or butt joins, and consolidation of the internal crizzling. The experimental methodology first utilized a series of facing mock-ups, assessed for strength, retreat-ability, and flexibility. Secondly, consolidation was evaluated by adding chemical dyes to the same adhesives. The dyed adhesive was applied to degraded samples, and photomicrographs were taken at cross-sections to assess the levels of penetration into the porous material. The results informed the stabilization of the Lindbergh navigation board.
This project also reflects on the ethical dilemmas that interventive treatments bring to conservators. When deterioration is unavoidable and severe, we must balance the object’s inevitable loss with the inherent risks of intervention. Ultimately, an adhesive treatment cannot arrest cellulose nitrate deterioration. However, it could act as a temporary stopgap to allow handling, exhibition, or replication, extending the life and accessibility of the object. This case study includes the ethics, practicalities, and outcome of an interventive treatment for cellulose nitrate, and reflects on our decision to intervene.