INTRODUCTION
Manual development of radiographs is more complicated and more time consuming than automatic processing. Most veterinary practices now have automatic processors, but manual development; old fashioned as it is, may still well crop up in the examinations. It is therefore important to be familiar with both techniques - not just the method employed at your own practice.

TECHNIQUE

1. Switch on the processor at the mains, allowing enough time for it to reach the correct temperature before use (20° C). Put on protective apron and gloves.
2. Check the levels of developer, stop bath and fixer BEFORE use and replenish if necessary.
3. Stir the developer well in order to mix the emulsion, but do not be over vigorous as this will cause the formation of air bubbles which may leave undesireable artefacts on the developed radiographs.
4. Ensure that the work bench is clean and dry, and that there are adequate supplies of film and hangers.
   Two types of hangers are available; channel hangers and clip hangers. The channel variety are much less fiddly to use and therefore less likely to contribute to fingerprints and abrasions on the exposed film.
5. Check that the safelight is operational and that the filter is of the correct type for the films in use.
   Brown/amber filter for blue light sensitive film; red filter for green light sensitive film.
6. Now you are ready to develop your films. Lock the darkroom door, switch on the safelight and switch off the main light.
7. Open the cassette and carefully remove the exposed film handling only with clean, dry hands and at the very perimeter. Never leave the exposed film lying around whilst you reload the cassette; always insert it into the hanger and place in the developing tank first. Once the film is within the hanger it should not be handled; use the handle of the hanger to transfer the film to the necessary area.
8. Develop the film according to the manufacturer's instructions; usually 3-5 minutes; always use a stop-watch - never estimate, as 3 minutes can seem like an eternity when you are alone in the darkroom!
9. Close the lid of the developer to prevent oxidisation and fogging. Whilst development is in progress, reload the cassette with a new film.
   A favourite examination question is to name the chemical reaction that occurs during development - this is "reduction" and occurs when the silver bromide crystals of the x-ray film undergo chemical change to become metallic granules of silver (which show black on the exposed film); the bromide is released into the developing solution.
10. Agitate the hanger gently within the developing tank periodically to ensure that the film is evenly coated with fresh developer.
11. Remove the hanger and transfer to the stop bath; agitate for 10 seconds.
    The stop bath is commonly filled with water, and this serves to arrest the developing process and prevent contamination of the fixer by the developer. A weak acid solution may be preferred since this is more compatible with the fixer (also acidic) and more efficient than water at stopping development due to the alteration in pH.
12. Now transfer the hanger to the fixer. After 30 seconds, the film will be safe to view. However, clearing (the removal of undeveloped halides) may take up to 3 minutes so it is prudent to wait a little longer or the film may still have a milky appearance.
13. Fix for a further 15 minutes to ensure that hardening has taken place.
14. Place the hanger in fresh, clean, constantly flowing water for half an hour to remove any residual chemicals. Insufficiently washed radiographs may be subject to yellow/brown stains.
15. Remove the film from the hanger and allow to dry in a clean, dust-free environment before placing into a labelled envelope.
    See Practical Task: Automatic Processing for the labelling requirements.
16. Ensure that the work bench is clean and dry, cover the developer (this should always be covered except when in use), drain the wash water and switch off the lights.