Operating Manual

10
Processing and
storage of X-ray films
85
Film developing is the process by which a latent image, see section 7.2, is converted into
a visible image. The crystals in the emulsion - carriers of the silver traces forming the
latent image - are transformed into metallic silver by selective reduction as a result of
which the visible image is created. The development procedure must be carried out
carefully to achieve this and guarantee successful archiving over a longer period.
Manual developing is a laborious process that must be carried out meticulously in order
to get the high quality results.
For increased efficiency and uniform quality, X-ray films are more commonly processed
automatically. The manual process is, however, still frequently applied.
It will therefore be useful to describe manual processing in this chapter and so become
familiar with the developing process.
10.1 The darkroom
Entrance and colour
For practical reasons the darkroom needs to be as close as possible to the place where
the exposures are made, although naturally out of reach of radiation.
The darkroom needs to be completely lightproof, so the entrance must be a “light-trap”
usually in the form of two doors, (one after the other), a revolving door or a labyrinth.
In practice the labyrinth is found to be the best arrangement, although it does take up
a comparatively large space. The walls of the passage are painted matt black, and a
white stripe about 10 cm wide running along its walls at eye-level is enough as a guide.
Inside the darkroom itself, the walls should preferably be painted in a light colour; light
walls reflect the little light there is and are easier to keep clean.
Darkroom lighting
X-ray films are best-processed in normal orange-red (R1) or green (D7) darkroom
lights. The distance between film and darkroom lighting needs to be considered, depen-
ding on the sensitivity of the film and the duration of the development process.
The “light safety” of the darkroom lighting can be tested by covering half of a pre-expo-
sed film (density 2) lengthways, leave it for 5 minutes and then process it as usual.
The difference in density may not exceed 0.1.
84
Preparation for an X-ray exposure of a painting by Rembrandt