Canis ISSN: 2398-2942

Radiography: film faults

General faults

Fogging

Cause
  • Generalized:
    • Chemical fogging.
    • Heat.
    • Film beyond 'shelf life'.
    • Safelight intensity too high (should be <25 W) or safelight too close to bench.
    • Safelight filter damaged or does not correspond to sensitivity of film.
  • Localized:
    • Film storage box not closed properly before switching on white light or opening darkroom door.
    • Pressure on films during storage.
    • Light switched on before film fully fed into automatic processor.
    • Cassette damaged so that light leaks in.
    • Damp storage conditions.
    • Cassette stored near x-ray machine or left on table during another exposure.

Remedy

  • Store films in cool dry conditions.
  • Ensure darkroom is light proof and safelighting appropriate.
  • Check cassettes are light proof and discard any which are damaged.

Static electricity marks

  • Black forked lightning marks Film faults static electricity on the film.

Cause

  • Build up of static electricity.
  • Exacerbated by low humidity.

Remedy

  • Handle film carefully to minimize static build up.
  • Clean screens regularly to avoid static build up.

Crimp marks

  • Usually small black crescent shaped marks Film faults crimp marks on film.
  • May be white if made before exposure.

Cause

  • Rough handling of film when transferring in or out of cassette.

Remedy

  • Avoid creasing film.
    Tip film out of cassette rather than pushing at corners.

Screen marks

  • White marks on the film.

Cause

  • Dust or dirt on the screen, or foreign bodies in the cassette, preventing light from screen from reaching the film at a particular point.

Remedy

  • Clean screens regularly.

Other

  • Damage causing removal of areas of emulsion from film.
  • Finger prints Film faults poor washing caused by dirty or greasy fingers, eg handcream contacting undeveloped film.
  • Roller marks - linear marks on the film.
  • Scratches in film emulsion Film faults scratched emulsion caused by hangers, hopper, cassette and careless handling.
    Emulsion is particularly susceptible to damage when wet.

Cause

  • Build up of dirt or gelatine on rollers.

Remedy

  • Use care when handling film.
  • Clean rollers regularly and service processor periodically.

Exposure faults

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Image density faults

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Processing faults

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