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  1. #41
    Rudeofus's Avatar
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    Quote Originally Posted by mr.datsun View Post
    In theory could a developer develop the silver halides to max dMax at first run through?
    If the film area is sufficiently exposed ... and that's key: few scenes will give you that. The characteristic curve goes waaaaaaaaay up.

    Quote Originally Posted by mr.datsun View Post
    I see your point, but in my case the R09 was used for 10 minutes and Dokumol for 12 minutes and the R09 needed less hypo.
    But how fast did they do most of their work? Is there significant difference between 3 minutes of Dokumol or 12 minutes?

    Quote Originally Posted by mr.datsun View Post
    On a similar theme, will hypo reach an exhaustion point?
    Most certainly, especially when it is as dilute as it is in reversal developers. Also note that for every Silver ion bound by Thiosulfate/Thiocyanate/whatever a free Halide ion enters the developer. In case of photographic film that means Bromide or Iodide, and both counteract fixer action and development.
    Trying to be the best of whatever I am, even if what I am is no good.

  2. #42
    Jim Taylor's Avatar
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    Quote Originally Posted by Rudeofus View Post
    Also note that for every Silver ion bound by Thiosulfate/Thiocyanate/whatever a free Halide ion enters the developer. In case of photographic film that means Bromide or Iodide, and both counteract fixer action and development.
    Rudeofus - this is interesting. So - is there something to be done to quench or otherwise sequester those pesky free-halide ions? Or is it as simple as ensuring there is sufficient 'excess' developer to mitigate this?
    Cheers,

    Jim.

  3. #43
    Rudeofus's Avatar
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    Quote Originally Posted by jimbop View Post
    Rudeofus - this is interesting. So - is there something to be done to quench or otherwise sequester those pesky free-halide ions? Or is it as simple as ensuring there is sufficient 'excess' developer to mitigate this?
    Not really, and this will eventually kill every fixer even if you somehow remove/recover the Silver. Note, that not only the solvent liberates halide ions: where do you think they go when you develop silver?
    Trying to be the best of whatever I am, even if what I am is no good.

  4. #44

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    Hi All,
    In processing a roll of FP4 reversal last night, I realised that I'd not noted down the second exposure time in my intructions. This is in fact 3 mins per side whilst rotating the reel under water.
    I should also have noted that it's a good idea not to wear any clothes that you value, as potassium permanganate leaves a brown stain that is impossible to remove!
    Another observation is that I've not found using filters to try to enhance clouds to be very successful, as they tend to give an overall mudiness. A pale yellow helps a little, but I certainly wouldn;t use orange with this film/process. However, the process does seem to render cloluds and dramatic skies very effectively anyway.
    Finally, whilst I'd say that the success rate percentage-wise is probably comparable with shooting colour transparencies.
    Finally (OK, I've already said that but here goes) as with colour transparency film decent light makes a world of difference to the end result.
    Best wishes,
    Steve

  5. #45

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    Steve: you can eliminate the permanganate stain if you dip your clothes in a metabisulfite solution, much like you do with the clearing bath.

  6. #46
    Rudeofus's Avatar
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    Quote Originally Posted by Alessandro Serrao View Post
    you can eliminate the permanganate stain if you dip your clothes in a metabisulfite solution, much like you do with the clearing bath.
    There is a good chance that the Permanganate destroys fabric or dyes when it gets reduced to brown MnO2, which means you can remove the brown stain but still end up with stained clothes. This simple device, on the other side, should take care of all stains
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #47
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    Developers -

    p-amino phenol hydrochloride, which is the main developing agent in rodinal, tends to have this brown color in the final image. There are several important factors when it comes to final image color. Even a new agent from another factory can cause color-tone shift. Other things as simple as the water you use +++, etc.. The best neutral result "with the developers used": I would stick to a developer [1st & 2nd] with a high concentrate of HQ and sulfite. Most films will have a good 'neutral' with such a developer.

    dw

    dr5.com

  8. #48

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    Why does the developing agent stay on the film, after developing/fixing/rinsing ?

  9. #49
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    There are multiple sources of brown in an emulsion: it could be brown stain (think pyro developers), it could be some form of fog, or it could be tiny silver crystals which carry important image information. A bleach will get rid of brown image in the latter two, but in the last case you don't really want to. Since DR5 suggested that Rodinal is no good for reversal development, I suggest everybody follow his advice and look at more suitable developers for B&W reversal. I don't think many here can match DR5's practical experience with b&w reversal ...
    Trying to be the best of whatever I am, even if what I am is no good.

  10. #50
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    I can hardly blame DR5 for not giving away his trade secrets, quite to the contrary, I'm impressed he responded here at all.

    I do have a theory about Rodinal and brown silver: in the FD step you have a strong solvent which completely removes tiny grains but leaves not so tiny grains behind as tiny grains. Tiny grains would normally either
    • not develop at all because they are very insensitive to light
    • be dissolved away by any moderately solvent developer

    Now all of a sudden we have a strong re-exposure step which makes sure these tiny grains are exposed and will develop, too, and we have a more or less non-solvent developer (Rodinal) which happily develops them into tiny (and therefore brown) Silver crystals. DR5's suggestion to use a developer high in HQ (i.e. high contrast, i.e. won't develop tiny grains) and high in Sulfite (i.e. dissolves tiny grains before they develop) would certainly point in that direction.
    Trying to be the best of whatever I am, even if what I am is no good.

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