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Old 20th March 2016, 03:04 PM
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AlonewithmyBW AlonewithmyBW is offline
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Default Stupid question time...

Can you over fix?

I get a bit of a panic about this, and tend to leave film in the fixer for a while. It is a bit of a 'just to be sure' reaction probably due to inexperience.

Can I cause any harm to the negatives if I leave it fixing for an extended period, and what might be the results?
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Old 20th March 2016, 03:21 PM
Richard Gould Richard Gould is offline
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Over fixing should not phsycally harm the negatives, but what it can do is lose fine detail in the negatives as they can sort of bleach out, and the longer the fixing the worse it can get, For films in 1/4 the max time would be 3 minutes, with the exception of the Tmax films, which need twice as long, the rule of thumb is to fix for twice as long as the film takes to clear, I tend to standardise on 3 minutes, to check the effectiveness of the fixer use the film leader of a 35mm film and when the clearing time extends to twice as long as fresh fixer then discard, I mix 600ml @1/4 and use it 8 to ten times then discard and mux fresh.
Richard
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Old 20th March 2016, 04:07 PM
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AlonewithmyBW AlonewithmyBW is offline
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Thanks Richard.

I will be more cautious, I have been fixing about 8-9 minutes in a 1/4 solution on Fomapan film. Not noticed any detriment but if it is subtly causing issues then I wouldn't see the problem!

Will reduce the time in the fixer from now on.
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Old 20th March 2016, 04:34 PM
Richard Gould Richard Gould is offline
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I use Fomapan 400 as my main film and at 1/4 the film is cleared after 30 seconds agitation, so would be fixed in 2.30, 8/9 minutes would be way too long, you would almost certainly find that some of the detail would go in that time, 3 minutes is the max time for fixing,
Richard
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Old 20th March 2016, 05:18 PM
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Martin Aislabie Martin Aislabie is offline
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I know the OP is about fixing film but its worth saying one should avoid over-fixing prints.

Getting the waste products in the fixing solution that soak in to the prints paper base is difficult - so don't over-fix and this eliminates the opportunity for the waste products to build up in the first place.

Incidentally, Tim Rudman in his (excellent) toning book claims that the length of time prints spend in the fixer can affect their colour when toned.

Martin
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Old 20th March 2016, 06:19 PM
Lostlabours Lostlabours is offline
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Quote:
Originally Posted by Martin Aislabie View Post
Incidentally, Tim Rudman in his toning book claims that the length of time prints spend in the fixer can affect their colour when toned.

Martin
Over fixing removes the finest silver grains first and with prints can have a marked effect with warm-tone papers both to bleaching highlight detail and also the final un-toned image colour. It also greatly reduces the fixers capacity.

Ian
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Old 20th March 2016, 10:47 PM
John King John King is offline
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It is/was also accepted that the longer you fix a film or paper then the washing stage should be extended as well.
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Old 20th March 2016, 11:41 PM
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Ilford recommend 2-to-5 mins I have always fixed my film for 5 mins and never had any trouble


www.essexcockney.com
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Old 20th March 2016, 11:56 PM
Mike O'Pray Mike O'Pray is offline
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This is only anecdotal based on what I think I have read over many posts but it might depend on the film. Some argue that TMax films need longer. I think it was Harry Fearn in his book "Better in Black and White" who said that TMax films need about 9-10 mins. Others argue that "normal" fixing time of say 5-6 mins is OK with TMax but you need to discard fixer quicker than with say Ilford films

I usually use 6 mins which includes a kind of safety margin i.e. it may be too long but avoids any overfixing.

I think I had read that up to 10 mins should not incur problems.

Try say 6 mins fixing then examine those negs against the 8-9 mins you have used and see if you can detect any difference in them and of the prints from them.

Mike
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Old 21st March 2016, 11:39 AM
namir namir is offline
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Sometimes instruction leaflets are really helpful:
Quote:
Film clearing time
In order to avoid the risk of insufficient fixing. film should remain in the fixer for twice the time it takes the emulsion to clear. Fixer should be discarded when the clearing time in used fixer exceeds twice the clearing time in fresh fixer.
The clearing time of a film and fixer combination can be found by the following method. It can be carried out in normal lighting. Take a piece of scrap unprocessed film and place a drop of the working strength fixer on to a small part of the emulsion side. Leave it until the
emulsion under the drop is a clear spot, this should take around 30 to 60 seconds. Immerse the piece of film in the fixer bath and using a stop clock time how long it takes for the rest of the film to clear. Clearing can be judged by comparing the surrounding film area with the clear central spot. The time taken for the rest of the film to clear
is the clearing time. The fixing time needed is double the clearing time
cf. http://www.ilfordphoto.com/Webfiles/...0218312091.pdf, p. 4.

The leaflet only says double clearing time, afaik for T-Max/Delta/Foma T it should be clearing time*3. I always try to be on the save side, so I fix slightly longer, with the fixer I use at the moment (mixed 1+4) it normally takes between 1-4 minutes, depends on the film and on how many films are through already, maybe sometimes 5 or 6 minutes

Last edited by namir; 21st March 2016 at 11:40 AM. Reason: Gerenglish
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