potassium bromide as anti-fog for negatives

Discussion in 'B&W: Film, Paper, Chemistry' started by Auroraua, Mar 14, 2014.

  1. Auroraua

    Auroraua Member

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    I bought some old films that are likely to be fogged, or at least there is a risk of it, so I bought Photography Formulas potassium bromide.
    It comes in crystals, and no instructions.
    How much of it would you use and would you mix it with the developer - such as Rodinal 09 or Rodinal Special One shot.
    I could weigh up the crystals let´s say 2 grams or 5 grams - how much water would you recommend - which dilution?
     
  2. Athiril

    Athiril Subscriber

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    I haven't added it to existing B&W developer before, but I've added 10g/L to C-41 and processed at a 2 stop 'push' (4m 15s) and with 2 stops of overexposure before with good results.

    How old is the film? You're going to need a test.
     
  3. Ian Grant

    Ian Grant Subscriber

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    It's not usual to ad Potassium Bromide to film developers, it's unlikely to help much and you can print through any increased based fog. With papers adding bromide reduces the sensitivity meaning you need increased exposure.

    In addition some film developers are very sensitive to increased bromide levels, it inhibits the action of Metol, it may well have a similar effect on the p-Aminophenol in Rodinal, but would have far less effect with Rodinal Special which is a PQ developer. Phenidone is restistant to much higher levels of Bromide.

    Ian
     
  4. Athiril

    Athiril Subscriber

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    Ian; you can lower the fog level in films with KBr, even if the fog level density is say 1.5, you can get it back down again.
     
  5. Xmas

    Xmas Member

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    which dev have you tried?
     
  6. Athiril

    Athiril Subscriber

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    C-41, E-6 first developer mostly. I've done random tests on B&W with own dev and seeing how much density I could pull down.

    See here, this is the last one I've done - http://www.apug.org/forums/forum40/128095-dealing-fogged-e-6-film.html

    If I can pull down fog hard on C-41 and E-6 (E-6 first dev is a B&W negative developer) then you can certainly do it on B&W film.
     
  7. Rudeofus

    Rudeofus Subscriber

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    There is no correct value for Potassium Bromide addition in film developers, since your film is out of spec and nobody can know for sure how much is needed to get fog level back down. Fortunately you can find out the correct amount for your combination of film&developer with little effort:

    • In complete darkness put a short, unexposed clip in your film tank. There is no need to put the clip on the spindle, but make sure you have that black tube in your tank in the correct position, or light will come into the tank through the lid.
    • Take just as much developer as needed to completely immerse the test clip and do a test run with this setup. Stop, wash, fix, wash again, then inspect the test clip.
    • If that first test clip is not significantly fogged, you can develop without any extra restrainer.
    • If that first test clip is noticeably fogged, start with 2g/l Bromide and do the test again.
    • If the second clip is still fogged, go up to 5g/l, if it is completely fog free, retry with 1 g/l. If there is only weak fog, you are fine with 2 g/l.

    Since your film is fogged from old age and/or improper storage, there is no need to fine tune the amount of KBr, since there will be some variation between film rolls anyway. If you want perfect and reproducible results, use fresh film ...

    PS: If Bromide had no effect on Phenidone based developers, then please someone explain me why they put it in E6 FD. And in Crawley's FX-37. And in ID-68 aka Microphen ...
     
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  8. Gerald C Koch

    Gerald C Koch Member

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    I agree with Ian that using potassium bromide is not needed. In addition film losses speed with age and the bromide will also cause a loss of film speed. So not a good idea.
     
  9. RalphLambrecht

    RalphLambrecht Subscriber

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    KBr is a known anti fogging agent in edev formulaeas it buffers development,adding it toexisting formulae is likely to upset the fine balanceof ingredients and could impede development beyond your wishes.if you insist to try,I'd start with no more than 0.5g/land increase by the same amount until you get your desired result.good luck.:smile:
     

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  10. Ian Grant

    Ian Grant Subscriber

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    PQ developers are tolerant to much higher Bromide levels, this is because the Bromide doesn't suppress the activity of the Phenidonne but it does suppress the Metol in MQ developers.

    This is particularly important where developers are replenished, Autophen a commercial PQ version of D76/ID-11 had far greater capacity and could be replenished by a topping up method rather than the bleed & top up needed with D76.ID-11.

    So Bromide is more effective in a PQ developer as a restrainer without causing any speed loss hendce why it's used in the developers you mention.

    Ian
     
  11. Ian Grant

    Ian Grant Subscriber

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    A note about C41 and E6 developers, apart from amateur kits they are designed for continuous replenishment and the consequent build up of Bromide and Iodide.

    Ian
     
  12. michael_r

    michael_r Subscriber

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    Rudi, you're correct bromide does restrain Phenidone at the pH values typical of fine grain developers. At higher pH values Phenidone is less sensitive to bromide and BZT is more effective (hence it's use in Phenidone-based print developers).

    As for FX-37 on the other hand (which contains both bromide and BZT) I believe the presence of bromide has more to do with Crawley's view that it improves definition in developers containing borate alkalis (which FX-37 does, along with Carbonate).
     
  13. Ian Grant

    Ian Grant Subscriber

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    No Michael that's where you're wrong. Ilford did a lot of research into the effects of Bromide on MQ and the equivalent PQ fine grain developers (ID-11/D76 variations) and the PQ versions are remarkably tolerant of Bromide build up which has far less effect on restraining development.

    Ian
     
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  15. Athiril

    Athiril Subscriber

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    Bromide isn't speed losing, it's contrast increasing by lowering density, more at the lower exposure scale than the higher scale. It's all in how you use it.
     
  16. michael_r

    michael_r Subscriber

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    Ian, Phenidones are indeed less sensitive to bromide than Metol, but there is still some restraining action. Most mildly alkaline PQ developers would produce higher fog than comparable MQ equivalents without some KBr in the formula.
     
  17. Auroraua

    Auroraua Member

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    Thanks for the replies

    Rudeofus
    What dyou mean with?
    "There is no need to put the clip on the spindle, but make sure you have that black tube in your tank in the correct position, or light will come into the tank through the lid."

    ​I have one of these stainless steel ones. Can´t I open the small lid to pour the liquid in?

    Although I´m still not sure as of what to do.
    I don´t really have a stock of old films to test with, it was more a case of trying to put something in when I suspect the film might be fogged and then it´s a trial and error. But it might be that 2g/l is the way to go.
     
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  18. Xmas

    Xmas Member

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    @Auroral

    the plastic tanks need the tube but normally stainless are different.

    @Michael 19...

    Yea most of the Phenodine (and their analogs) formula's have halogen restrainers (as do some of the metol formula eg for D76 'clones'.

    But with some films the fog level in the MQ is higher and increases more rapidly with time, comparing ID11 and ID68.

    And as Ian mentioned replinisher rules can be different.

    But adding 1g/l to a PQ ID11 clone won't make much difference compared with a MQ variant so the restrainers are not independent of dev type (or independent of pH of a developer).

    I have oodles of old cine and use stock microphen or ID68 gave up on adding more restrainer simpler altering ISO a stop and dev for 15% less time, don't use MQ cause of skin problems.
     
  19. Rudeofus

    Rudeofus Subscriber

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    If you have no film to test a modified developer with, I'd say leave out the extra restrainer and print/scan through the fog. As I mentioned before, there is no "correct" amount of restrainer for aged film, it is completely up to tests and experimentation.

    About the tank&lid: if you were to make tests, you want to use as little film and developer as possible. If you put a test clip onto the spindle of an inversion tank, you'd have to fill that tank with developer, which means 250 ml per test. If you instead put a small test clip onto the bottom of your tank and leave out the spool, you may get away with 50-80 ml of developer per test run. The note about the spindle is specific to plastic tanks: even if you leave out the spool, you must still put the spindle in its place or light will come into your tank. I don't know or use stainless steel tanks, so I can't tell you much about them.

    There is one way you could still do tests without sacrificing a whole roll: leave the first few image frames unexposed and use that area, clip by clip, for testing various amounts of KBr.
     
  20. Rudeofus

    Rudeofus Subscriber

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    Athiril, if you need more exposure to reach b+f+0.1 density, and require less development to get the specified contrast, then you will most definitely lose a fair bit of ISO speed.
     
  21. Photo-gear

    Photo-gear Member

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    I have foggy a bulk roll (100') of expired Plus-X Pan [2003]. After reading your post, I am wondering what could be the formula for developping this film, using PQ developer + KBr. I wish I could get an answer to it. Thx!
     
  22. Ian Grant

    Ian Grant Subscriber

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    There isn't really an answer, you need to use a clean working developer and do some tests, personally I wouldn't bother as the omages I make are precious to me and can't be retaken (well not identically anyway - unless a studio setup).

    Ian
     
  23. Auroraua

    Auroraua Member

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    PQ developers I understand are based on Phenidone
    and Mq based on metol
    Could you name a few examples of developers that are MQ PQ?

    PQ - ID11.

    What is HC-110?

    I have HC110, Rodinal and Rodinal Special. Where I live they only have a couple of Ilford ones - in the whole country...
    Which is why I need to buy ahead of time.

    So with the old cine stock, you just do it all at box speed and hope for the best?
    Well if you have a stock - it´s useful.

    I am happy to experiment and try out different versions, but for example with this 120mm - it is just one - it´s not really worth it.
    Will recompile the info I got and report back with the result.
     
  24. Athiril

    Athiril Subscriber

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    That's a big if, especially if you start defining the reduced contrast of fogged film as box speed, which I would not.

    If your film at a developing time of A has a dMin of 1.0, and a dMax of 1.3, and with x g/L KBr added a developing time of A has a dMin of 0.2 (where fresh film is say 0.1, so there is still some fog there) and dMax of 1.0, and at A+30% with x g/L KBr added has a dMin of 0.3 and dMax of 1.3, I wouldn't start calling it a speed loss.
     
  25. Rudeofus

    Rudeofus Subscriber

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    ID-11 is the same as D-76, which is MQ. HC-110 is a PQ type developer. While the HC-110 formula is proprietary, there are published formulas for many other developers, see here for many examples.
     
  26. Rudeofus

    Rudeofus Subscriber

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    Athiril, I think we just mixed up developer speed and emulsion speed. I was talking about the latter, and Bromide is unlikely to increase it. I have no opinion about developer speed.