Selecting Material for Digitisation: Glass Slides and X-ray acetates

Part of my role for the project is to select relevant material from the Biophysics collection for digitisation. The Biophysics collection of paper, glass plate and acetate photographic material produced by staff members and spans from the department's inception in 1947, to 1984. My brief was to select a subset of 4000 images from this collection relating to DNA research carried out by Maurice Wilkins and others.

The bulk of the images came from the quarter plate glass plate negative collection that comprises of 18300 individual items. While DNA research accounts for a significant proportion, other departmental work notably on muscle and the structure of collagen are also represented. The DNA related slides had to be handpicked from this larger total. Fortunately, the entire series had been indexed by the department. During the cataloguing project in 2011, these index books were digitised and transcribed into a spreadsheet, which made the task of selection much easier. 

Example of index entries for the quarter plate glass negatives: The entry referenced as "867" is of particular interest as this refers to "Photo 51", the best image of Structure B DNA produced by Rosalind Franklin.

The selection criteria used was based on my own understanding of the collection and the brief of the project. Having worked on the cataloguing project of the papers prior to this role, I felt confident in my ability to determine which material should be included. For the most part this was fairly academic as each slide indicated who created them and all material from well known DNA researchers was selected (e.g. Wilkins, Franklin, Gosling, Wilson etc.). When the creators’ relationship to DNA research was not so obvious, such as visiting academics or PhD students, then I consulted the catalogue to see whether they collaborated in DNA research. I decided to include all work (not just DNA research) in the early years of the department as often related project techniques and microscopy work helped shape the later DNA research. Supplementary material relating to microscopy studies, chemical analysis and model building and a smaller number of half plate glass plate negatives and photographic prints were also included.

An example of a quarter plate glass negative: This image was referenced in the index as "2747" and shows an x-ray diffraction exposure of lithium (Li) DNA in a B configuration created by Maurice Wilkins in April 1958.

The jewel in the crown so to speak was the third main source of material - the x-ray acetates. Remarkably, some of the original x-ray exposures have survived and capture the various samples, salts and techniques that the KCL Biophysics department used in their x-ray diffraction studies of DNA and later RNA and nuceleoproteins. It was decided early on that all the x-rays were to be digitised, due in part due to their intrinsic value but secondly because of their unstable physical condition. Acetate film has a tendency to deteriorate and undergo what is known as vinegar syndrome. This is when the acetate degrades and begins to oxidise creating a vinegar smell. The surface often begins to warp and crack and fades the original image. The condition is autocatalytic which means that once it has begun it cannot be stopped with the only stabilisation solution being to isolate and freeze the material. Many of the x-rays show the early signs of this condition (small pock marks) but the vast majority have retained clear x-ray patterns.

X-ray diffraction exposure showing clear warping and peeling of the emulsion layer but retaining the x-ray pattern of DNA.

X-ray diffraction exposure of DNA with typical pock marks associated with acetate deterioration

Digitisation is the best strategy for long term preservation of this material for several reasons. Firstly, by producing a digital copy we can retain valuable content before further deterioration ensues. Secondly, the digital copy will be more accessible than the original as a high quality scan can provide a greater degree of clarity than the physical copy and thirdly by producing a digital surrogate it reduces the risk of damage from physical handling and allows for the original material to be put into cold storage. 

Overall, the images selected from the Biophysics Department are representative of the biophysical approach to genetics taken between 1947-1969.The collection provides an unprecedented record of x-ray diffraction studies in genetics as well as fully documenting the experimental work of Maurice Wilkins and his colleagues carried out at King’s.