Anti fogging agents- effects and developer types

Discussion in 'B&W: Film, Paper, Chemistry' started by jamie young, Mar 25, 2014.

  1. jamie young

    jamie young Member

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    I'm using a lot of older film these days for my panoramic photography. Some is aerial film. I want to understand anti fogging agents and their effects in order to minimize the base plus fog build up with these older films.I thought I would start with benzotriazole. How does this affect contrast and speed when you use it. Any other problems I need to know about? I usually use roll pyro for development. Is it compatible. Anyone have any good reading material they could recommend on this?
    Thanks! Jamie Young
     
  2. Anon Ymous

    Anon Ymous Member

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    While we are at it Jamie, perhaps you wouldn't mind me asking something relevant. Given the fact that benzotriazole is used in cool tone print developers and that cool tone is a result of large grain, would it be a good choice for film developer antifoggant? Would KBr, which gives warmer tone (finer grain) in prints be a better choice?
     
  3. jamie young

    jamie young Member

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    It's known to be and excellent antifoggant, hence my mention in this post. That being said, I've never used any anti fogging agent and am asking for advice on the subject. I'm using it for film and not interested in tone changes.
     
  4. Axle

    Axle Member

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    Benzotriazole is the only anti-fog agent I know, and one I've used myself, add that to a strong developer (Xtol or D-76 stock) and you'll have little issue with fog.
     
  5. cliveh

    cliveh Subscriber

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    Why do you think benzotriazole is used only in cool tone print developers? This is not the case.
     
  6. Xmas

    Xmas Member

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    The BZT and KBr will slow the development their effectiveness is dependent on developer ie the agent eg metol and pH but they are not magic bullets.

    If the film fogs uniformly you need to print through it.

    Reduce ISO a stop and time in dev by 20% may be best gambits while you experiment.
     
  7. Athiril

    Athiril Subscriber

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    You can add anti-foggants/restrainers, and increase developing time to cut fog effectively.
     
  8. Anon Ymous

    Anon Ymous Member

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    I don't. I'm only asking if it is a good choice, regarding the granularity of the processed film. Still if it's the only reliable option, that would be an acceptable compromise.
     
  9. Xmas

    Xmas Member

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    I dont think it is simple eg if you dose DK76 with KBr it will really slow it down whereas the same amount in Microphen may not make any detectable difference to negative at all. the base fog level might not change, in either case!

    If you have lots of negative material you are going to need to experiment Id start with a low fog dev and dose it with both KBr and BZT and soup a test shot

    Sweep the ISO from box to slower in 1stop steps meter for zone 1 you need to know the speed over fog at an acceptable fog level. If you develop for longer in my experience you get more fog...

    if you are lucky you will get a slower film with less range and fog you can print or scan through. BZT is toxic take care.
     
  10. Photo Engineer

    Photo Engineer Subscriber

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    In order of strength and effect on speed and contrast:

    BTAZ (Benso Tri AZole - thus the abbreviation), 5-Nitro Benzimidazole Nitrate, and Phenyl Mercapto Tetrazole (PMT).

    The first and last are available from the Formulary and last practically forever on the shelf and in solution.

    PE
     
  11. jamie young

    jamie young Member

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    Thanks PE! Could you elaborate on effect on speed and contrast. The films I'm developing are Vericrome pan (8" x 5' cirkut), plus x 2404, 3404, and forte 400 in 16" rolls spooled for 16 cirkut
    You input is appreciated
     
  12. Photo Engineer

    Photo Engineer Subscriber

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    I cannot comment as the effects vary rom film to fim and developer to developer. Just count on speed and contrast effects. That is about all I can say. Sorry.

    PE
     
  13. Xmas

    Xmas Member

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    the actual results you get will also depend on how foggy the film is as well you need to try each film type you have like a test strip in wet printing
     
  14. jamie young

    jamie young Member

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    Ok PE I'll experiment but I'm assuming you mean less speed and less contrast
     
  15. eclarke

    eclarke Member

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    Don't be heavy handed, especially with the benzotriazole..it can really slow down the film
     
  16. David Lyga

    David Lyga Subscriber

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    Try this:

    Mix 1 gram of Benzotriazole into a bottle containing 100ml of water. You have to shake the mixture mightlly because it does take a few minutes of such vigor to go into solution.

    Then, start by adding about 10ml of this BZ solution per liter of working solution developer. That is not much and might not give much solace with reducing fog. For heavily fogged film/paper, I use about 50ml per liter of working solution developer. The slowing down of development with this highest percentage addition is substantial, but not profound. Of the cuff, I would say that you must increase development by about 33% to 50% with this '50ml' addition. I do promise that you will be pleased with the results.

    My WORST film is Kodak Recording Film. I rate this old, heavily age-fogged stuff at about EI 16 and am pleasantly surprised with the lessoning of fog, even with the necessarily increased development needed to attain adequate contrast. Experiment and take accurate notes. Decide upon a particular developer (D-76 is fine) and stick with it so that results will become predictable. Different films might need different strengths of BZ added, but even with the max (ie, 50ml, or even MORE!) you can do ALL films even if, with lesser fog problems, that amount might be a bit wastful.

    NOTA BENE: Yes, BZ can also be used with COLOR film and paper developers to aid in age-fog reduction. HOWEVER, beware of the slowing down of development that a little BZ can do with color chemicals. Start by adding only about one tenth of the BZ solution which I advised to add for traditional B&W. (There are too many different situations out there for me to offer more precision to such quantification.)

    Finally, potassium bromide can ALSO be used instead of bensotriazole. Again, off the cuff, I would suggest using 10 times more (ie, 10g per 100ml water) as your stock restraining solution. This should then offer about the same effects as the BZ solution, so the ml additions to working solution developer will be about the same. - David Lyga
     
    Last edited by a moderator: Mar 27, 2014
  17. Gerald C Koch

    Gerald C Koch Member

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    Heating the water to 50C helps greatly with getting BZT into solution.
     
  18. Anon Ymous

    Anon Ymous Member

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    Ok nice tip, but what about its keeping properties in water, does it keep well, or should we use another solvent?

    TIA
     
  19. Gerald C Koch

    Gerald C Koch Member

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    It keeps very well as a water solution. Edwal marketed a product called Liquid Orthozie which contained 2.7% benzotriazole and ~5% sodium sulfite in water solution. The purpose of the sulfite is to improve the solubility of the benzotrizole and not as a preservative.

    There are better solvents than water such as ethyl or isopropyl alcohol and ethylene glycol but then the amounts of the resulting solution to be used are small and hard to measure. The advantage of the 1% solution is that the amount used is approximately the same as what is used for 10% potassium bromide.
     
    Last edited by a moderator: Mar 27, 2014
  20. David Lyga

    David Lyga Subscriber

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    +1: you will have no problem with BZ or PB keeping well in stock solution. Thank you for the percentages for Orthozite, Gerald. - David Lyga
     
  21. Xmas

    Xmas Member

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  22. sun of sand

    sun of sand Member

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    I use orthazite and for pretty foggy film I tend to add 5-10ml of orthazite and I believe I've found anti-fogging to be better when you combine kbr and btaz together
    Normally like 7ml orthazite 2.7% and 3-4ml kbr 1%
    Iodide in even smaller quanitites but I can't remember the amount ..maybe 1ml iodide with the btaz
    but maybe the %age was .1%
    don't remember what iodide did anymore if i could tell anything



    for the foggy film I've found my 7/2 anti-foggant to drop actual speed from 40ASA to 12ASA


    Chlorhydroquinone developers help a great deal with paper fog
    as in old almost useless papers become very usable with very little additional anti-fog procedures
    but chlorhydroquinone is impossible to find




    badly! mottled film along with age fog responded very well to Rodinol with my anti-fogging
    better than any other developer I tried
    ABC Pyro
    Xtol
    PMK
    D76
    D23
    all fairly sucked at reducing mottle
    ...
    Chlorhydroquinone paper developer I tried was only AS GOOD or at best marginally better than Rodinal with the film
    Now that I think about it I believe that mottled film was the reason I mixed up the Iodide.
    Rodinal with all 3 anti-foggants or iodide/btaz?
     
    Last edited by a moderator: Apr 15, 2014
  23. Mark Crabtree

    Mark Crabtree Member

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    It would be interesting to see how HC110 compares to those. It has a reputation for very low fog. It has given me my best results with outdated film. I wonder why that is?
     
  24. sgoska

    sgoska Member

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    PE: I am no chemical engineer so I hope you could clarify.
    Old Kodak formulas for SH-5 indicate using 6-Nibrobenzimidazole nitrate as Anti-Foggant #2.
    Newer sources, including Mason's Photographic Chemistry (1977) never use "nibro" but use "nitro" and they mention 6-Nitrobenzimidazole nitrate as an anti-foggant, more active than Anti-Foggant #1 (BTAZ).
    Further, 5-Nitrobenzimidazole nitrate's CAS number (27896-84-0), molecular weight and chemical formula match 6-Nitrobenzimidazole nitrate and many (internet) sources claim these two are synonyms for each other.
    (No one seems to sell the 6-Nitro form anymore, which is the reason for my inquiry.)

    Does the attachment of the NO2 in a different location on the ring (5 versus 6) have any effect on its chemical properties? Perhaps, they perform the same once they are in solution? Or, is there a conversion factor for substitution?
    Why did Kodak specify the 6- and not the 5-? Why did they use "nibro" instead of "nitro"?
    If there is a significant difference between "nibro" and "nitro" in the SH-5 formula, I'd like to know. (I'm assuming it's like the difference between "bicromate" and "dichromate" or something like that.)
    Thanks for your help.
     
  25. Photo Engineer

    Photo Engineer Subscriber

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    Nibro is a misprint. Nitro is correct, and the substitution position (5 or 6) is important but in this case, IDK how important. If it is not available there must be a reason. I would not worry too much and just use something else.

    PE