Prewashing film

Discussion in 'B&W: Film, Paper, Chemistry' started by colrehogan, Mar 10, 2005.

  1. colrehogan

    colrehogan Member

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    How does prewashing film affect it? I thought it was merely to remove the anti-halation layer and makes the film more receptive to the developer. I've read in various places how you shouldn't prewash the Ilford FP4/HP5, yet I do and haven't had any problems that I know of. Is doing this wrong? Am I losing contrast because of it? I do pretty much the same 1 min water prewash with all my films.
     
  2. jcausey

    jcausey Member

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    Ilford doesn't recommend a prewash, but I'm pretty sure they only do that because they don't believe it's necessary, not because they believe it hurts anything.

    I prewash all my films, both to help remove anti-halation layers (though the blessed elixir of Rodinal does that rather nicely on its own) and to help keep everything at a nice consistent temperature, and I'm a happy-scrappy hero pup.

    You should see the kool-aid green water that comes back out when I dump the prewash back out with Forte (Arista.edu) films!
     
  3. Wally H

    Wally H Member

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    I pre-wash films for two reasons:

    1) To help the film come to processing temp faster than otherwise...

    2) So that when developer is introduced it tends to cover the film in a more uniform manner. Sometimes developer can distribute itself unevenly on dry film and this can lead to uneven processing. Short development times will increase this risk. Air pockets are also less likely with a pre-wash. Air pockets can cause uneven developer distribution also.
     
  4. John Z.

    John Z. Member

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    Also pre-wash to remove the colored dye backing on some films. The prewetting and washing is most important to make he development more even.
     
  5. jim appleyard

    jim appleyard Member

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    I read somewhere that some modern films, probably the T-grained, contain a developing agent which could be washed out in a pre-soak. I think that is why it is not recommended by some film companies.

    Perhaps Roger Hicks will see this and chime in. He seems to know quite a bit about emulsions.
     
  6. john_s

    john_s Subscriber

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    I think that Ilford don't recommend pre-rinsing because it washes out some kind of wetting agent that is supposed to make development more uniform under some circumstances. That is confirmed by the pre-rinse water from HP5+ readily foaming (i.e. it looks as though it has detergent in it.)
     
  7. rjr

    rjr Member

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    Jim,

    I think you are referring to wetting agents in film emulsion, probably to speed up the penetration of developer into the emulsion and to guarantee a more even penetration in case your agitation scheme is poor - I know that Ilford uses these on some Delta emulsions, which you can notice by the foam that settles on the developers surface - no matter what developer you use.

    Pre-Soak is a similar method - since the emulsion is soaked with water, the penetration of developer is slightly delayed and it will soak in more evenly. Plus if you are not using one-shot developers but multiple-use or deep tank developers, presoak will protect these from contamination of the deep-blue anti halation and protective laquer used on Efke Rollfilms.

    There is a third use of presoak - Jobo recommends a 5min presoak (IIRC) if you apply your times for manual agitation on rotation developing.
     
  8. rbarker

    rbarker Member

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    I pre-soak my Ilford films, too, and haven't had any problems.
     
  9. Ed Sukach

    Ed Sukach Member

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    I think you will find that JOBO recommends a DRY 5 minute pre-warm as an added insurance against possible reticulation - especially important with C-41 or E-6 processing... where the processing temperature is significantly higher that ambient ~ depending ...

    I remember, from some time ago, that pre-soaking / wetting film was NOT recommended - something about emulsion swelling and degradation of the image.

    Personally, I DO pre-warm - or more properly, temperature stabilize (I use the JOBO CPP-2 for everything), and do NOT not prewet - on either film or paper.
     
  10. rjr

    rjr Member

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    Jobo rec: Pre-Warm or Pre-Soak?

    Ed,

    I wasn´t referring to color processing and I am fully aware of the common mistake to read pre-warm as pre-wash - did that myself when i used E6 chemistry (Tetenal) first time.

    Pre-WARM is mandatory with E6 and C41, pre-WASH is forbidden there and optional for BW.

    I remember that Jobo handled the topic on the US "Jobo Quarterly", which can be found online at

    http://www.jobo-usa.com/jq/jq9802.htm#3982

    To quote:

    "Go back to the history of the story, and the answer is clear. JOBO was looking for a SIMPLE way to get customers successful in their processing. The presoak provided that simple "common denominator" that enabled us to tell customers, "Presoak for five minutes then process normally."

    What Kodak did was an enormous amount of testing, and published the results. Neither method is right or wrong. They both work well. If you are currently presoaking your film and getting the results you like, then keep on doing it. If you are starting without a presoak and you like the results, then keep on doing it. As I’ve said before, photography is not a pure science- it’s really alchemy. Enjoy it."

    So, we are both right. ;-)
     
  11. Flotsam

    Flotsam Member

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    I found that this long presoak helped achieve more even development but I still had to reduce my developing times substantially.