Finding Safety in Notches: Using ATR-FTIR Spectroscopy and Industry Literature to Identify the Substrates of Photographic Negatives

In 2022 the Museum of New Zealand Te Papa Tongarewa (Te Papa) instigated a 12 month project to identify film substrates in the Spencer Digby / Ronald D. Woolf (Digby / Woolf) collection. The presence of cellulose nitrate or cellulose acetate was determined using Fourier transform infrared (FTIR) spectroscopy. During the initial stages of the FTIR analysis it was hoped that the recording of film notch code data with correlating substrates could potentially lead to identification without the need for testing. This approach proved ineffective due to the dissimilarities in the way film manufacturers employed notch codes. A shift in focus towards establishing a cut-off date for cellulose nitrate sheet film in the Digby / Woolf collection ultimately led to a vast reduction in the amount of testing required. The establishment of this discontinuance date was further reinforced by research into the photographic companies that exported to Aotearoa New Zealand during the period. A priority was to confirm if these manufacturers followed a similar timeline for ceasing the use of cellulose nitrate as a substrate.