TNA Blog: Assessing Deterioration in Film and Photographs - How Can Science Help?
A heritage science collaboration between The National Archives and the British Film Institute
Icon member Jacqueline Moon ACR, Senior Conservation Manager for Public and Academic Engagement at the National Archives, explains the collaborative heritage science project she is running with the BFI.
The National Archives (TNA) holds over 1000 years of iconic historical records, while the British Film Institute (BFI) is the lead body for film in the United Kingdom, promoting and preserving filmmaking and television. We have established a long-term partnership to preserve and maintain access to the BFI’s collection of public information films, and in 2016 this was extended to include collaborative heritage science research.
Both institutions manage large collections – literally millions of items – and each brings distinct expertise to the collaboration. The BFI is opening up film collections through preservation, digitisation and online content, while TNA is using scientific techniques to better understand the material properties, conservation needs and history of film and photographs. Both institutions hope to broaden their experience and share their findings throughout the archive sector. We are currently focussing on the BFI’s collection of very early British film, which they have been digitising for online access as part of the Unlocking Film Heritage programme.
The negatives used to produce photographs and moving pictures have been manufactured in sheet or roll form on supports including cellulose nitrate (CN, 1889-1950), cellulose acetate (CA, 1925-present day) and polyester (1955-today). Cellulose nitrate and cellulose acetate are both are prone to irreversible chemical and physical changes resulting in some well-known effects; they can yellow, mirror, blister, wrinkle, crack, stick or even turn to powder. Their life expectancies can be significantly shorter than some of our oldest paper and parchment records. In spite of these problems, much of our film collection appears to the naked eye to be in good condition.
To understand this better, conservation scientists at TNA have been using a range of analytical techniques to study film samples. These range from visual identification, polarising filters (polyester polarises light and produces red/green interference while both cellulose nitrate and acetate appear dark) and some destructive tests, including the burn test, which for obvious reasons can’t be used on collection material! Research has shown that some of these tests may not be as accurate as hoped, so in order to look more specifically at the condition of the film samples we are also using Fourier transform infrared (FTIR) spectroscopy. FTIR has been well used to study plastics, but our research hopes to apply it to large archival collections, and to develop a method for assessing degradation signs as an early warning system for collection managers, enabling them to identify deterioration processes before their effects become visible to the naked eye.
As part of the project a mobile heritage laboratory from University College London will visit TNA on 8th June; drop-in places are available. Conservators and conservation scientists will explain their work with film and photographs though practical, hands-on demonstrations of techniques including optical microscopy, polarising filters, ultraviolet radiation and chemical spot tests. A short film has also been produced to explain and promote our innovative research.
Icon would like to thank Jacqueline Moon and The National Archives for their contribution to this blog. Keep an eye out for the next TNA blog appearing here in a few months.
Lead Image: Studying film samples with a polarising filter; Jacqueline Moon
Image 2: Examining photographs with Fourier Transform Infa-red spectroscopy; Jacqueline Moon
Image 3: The burn test for cellulose nitrate; Jacqueline Moon