By now regular visitors will be familiar with the textured 3D laser scans and pathological descriptions we frequently put up to show the public what we are up to and what to look forward to when the project goes live later this year.
In addition to the 3D models and descriptions there will be radiographs (and CT scans). Some of the radiographs will be newly created for the project, something I have been working on for the last few months. We also will be digitising historic radiographs. At Bradford we have a scanner for digitising radiographs. It was used in the From Cemetery to Clinic project to digitise the radiography archive of leprosy patients produced by Jos Anderson almost 40 years ago.
We have a large archive of historic radiographs to digitise for Digitised Diseases. Historic radiographs provide excellent context for the discussion of health and disease. The x-ray was discovered by Wilhelm Röntgen, a professor of physics in Bavaria in 1895. It was immediately apparent that this technique would be of huge value for clinicians. In 1896 an x-ray department had been set up at the Glasgow Royal Infirmary, one of the first radiology departments in the world.
Early radiographs were recorded on glass plates with an emulsion. Just before the outbreak of WWI, the Eastman Kodak company developed a cellulose nitrate film for radiography. Cellulose nitrate was also the material used to make cinematographic film.
Essentially nitrate-based x-ray film is based on nitrocellulose (guncotton!) plasticised with camphor coated with an emulsion. It is highly flammable and potentially explosive and degrades easily, giving off toxic gases. This has obvious health and safety issues attached to it!
Luckily in the early 1920s safety film was developed for radiography. This comprised an emulsion on a cellulose acetate backing, which is much slower burning. From the 1950s to the present day polyester based films are used. These are much more stable and resist chemical and physical changes as it ages.
The video below from YouTube shows the difference between safety film (in this case 35mm cinematography film, but same principles apply) and cellulose nitrate film when it catches fire.
We were fairly sure that none of the radiographs we have were not cellulose nitrate based films. However, it is good practice to write complete a COSHH form and do a risk assessment before any digitisation work was carried out.
After looking at the older, more degraded films we were sure that none of the films were cellulose nitrate based. This is how we went about our assessment:
1. We removed the most degraded radiographic films to a fume cupboard so they could out-gas.
2. Wearing PPE we took out the radiographs and looked at them. Degradation in some cases was very obvious.
3. We know that from the early 1930s nitrate film and the word “nitrate” on the edge of the film. Safety film, either cellulose acetate or polyester, had the word “safety” on the edge. I found a few examples of the “safety” stamp, but no “nitrate” stamps.
4. Other radiographs had a manufacturer on. This radiograph from the 1950s is labelled “Ilford”, who make radiographic and photographic film. I was able to check that this stock was indeed safety film.
5. Looking at the dates and conditions of the radiographs in question we could rule out all of them being cellulose nitrate, as they were either too late (i.e. post 1933) or their appearance was not consistent with cellulose nitrate film. The example below shows a very wrinkled radiograph with “channeling”. It is quite brittle and has a feint vinegar smell, which is normal for old cellulose acetate radiographs.
Some of the radiographs are extremely brittle or warped, which will present interesting conservation and digitisation decisions later on, as they are not suitable for running through the radiograph scanner. We have a number of trained conservators on the project, including the PI Dr. Andy Wilson, who will make decisions regarding how these radiographs are treated in the coming weeks.
If we had found cellulose nitrate radiographs we are fortunate to have cold storage facilities here in Bradford. We also have the very excellent National Media Museum only a short walk away, who have experts on the storage of old celluloid film – luckily we didn’t have to contact them!
Film Identification, National Park Service, US Department of the Interior
History, Science, Preservation and Treatment of Cellulose Nitrate Still Film
Managing X-ray Films as Federal Records, National Archives and Records Administration, Office of Records Services, College Park, MD (2000)
Nitrate film, National Media Museum (nd)
The Dangers of Cellulose Nitrate Film, Health and Safety Executive (2013)