Operating Manual

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7. screen(s) in poor condition
8. foreign bodies (for example metal particles ) between film and screen
during exposure
9. small, clear, hollow spots (usually with dark edges) may occur when the emulsion
has been subjected to local attack of bacteria. This is generally the result of slow
drying in a warm damp climate, particularly if there are impurities in the wash water.
Clear lines or streaks
1. the film envelope has been scored with a pointed object before exposure.
2. film insufficiently moved during development
3. uneven drying (film has been carelessly wiped dry after washing)
4. drops of fixer or stopbath have fallen on the emulsion before development
Clear shapes
1. clear crescent shapes may appear when, before exposure, the film has been
bent between two fingers
2. fingerprints may occur when the film has been touched with dirty fingers,
contaminated for example with grease, fixer, stopbath or acid
Dark patches
1. drops of developer have fallen onto the film before development
2. drops of water have fallen onto the film before development
3. electrical discharge marks, especially at low relative humidity of the air
4. marks from mechanical damage to the emulsion after exposure
Dark lines or streaks
1. the emulsion has been scratched after exposure
2. the film envelope containing the film has been scored or written on
with a pointed object after exposure
3. insufficient agitation of the film during development
4. uneven drying
5. water or developer has trickled down the surface of the emulsion prior
to development
Dark shapes
1. dark crescent shapes (see “clear shapes” above); these are darker than
the surrounding area if the bending occurred after exposure
2. fingerprints: the film has been touched with dirty fingers
3. electrical discharge (see “dark patches).
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Grey fog (local or overall)
1. unsuitable dark room safelighting
2. excessive exposure to safelight (i.e. too long or too close)
3. film accidentally exposed to X-ray or Gamma-ray or to white light
4. heavy scatter
5. film out-of-date or stored under unsuitable conditions (ground fog)
6. extreme under-exposure compensated by excessive developing
7. exhausted or wrongly mixed developer
8. film cassette with film exposed to heat (e.g. sunlight, heat from radiators etc.)
9. cassette not properly closed (edge fog)
Yellow fog
1. prolonged development in badly oxidised developer
2. exhausted fixing bath
3. insufficient rinsing between developing and fixing
Note: It may take months before yellow fog becomes apparent.
Dichroic fog
(i.e. greenish-yellow by reflected light, pink by transmitted light)
1. developer contaminated with fixer
2. film insufficiently rinsed after development and subsequently fixed
in exhausted fixer
3. film stuck to another film when placed in fixer (in which case the development
continues in the fixing bath)
4. prolonged development in exhausted developer
5. film partly fixed in an exhausted fixing bath, exposed to white light
and then fixed again
Mottled fog
A greyish, mottled fog generally means the film is out-of-date or that it has been stored
under unfavourable conditions, e.g. in damp surroundings.
Whitish deposit
1. water used to make up developer or fixer too hard
2. wash water too hard
3. film insufficiently rinsed after development
Clear patches
1. minute round spots with sharp edges: the film was not kept moving
in the first 30 seconds of development
2. drops of fixer or water fell onto the film before development
3. marks from mechanical damage to the emulsion before exposure
4. marks due to rapid and uneven drying of the film (this occurs when there are
still droplets of water on the film when placed in the drying cabinet)
5. clear patches can occur from the film sticking to another film or to the tank wall
during development
6. grease on the film slowing down or preventing the penetration of the developer