Rehalogenation with a chloride?

Discussion in 'B&W: Film, Paper, Chemistry' started by Sparky, Mar 26, 2007.

  1. Sparky

    Sparky Member

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    So - I've been going through Rudman's Toner Book - which is great, by the way... and, what, with all this talk on chloride printing out papers and all... I got to wondering if one couldn't simply bleach out a bromide print and redev/rehalogenate with a chloride, leaving the silver intact - creating something perhaps not so far off from POP....

    The closest thing to approximate this, from what I understand in the rudman book, is the thiourea dioxide process (FSA)... but I'm just skimming for the moment - so I could be wrong on that.

    Anybody every try this?
     
  2. Photo Engineer

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    Nope, don't try rehal with chloride.

    PE
     
  3. Jordan

    Jordan Member

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    PE, what happens when you do?
     
  4. Photo Engineer

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    Silver chloride is too soluable and the image is etched away. You lose detail in the highlight areas. In fact, sodium chloride is a sliver halide solvent, with silver chloride at the top of the list. Basically, you have a mild blix.

    It works much faster as a bleach (blix) though. That I can say for it! The solvent action pushes the oxidation to the right.

    PE
     
  5. gainer

    gainer Subscriber

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    I can't argue with your logic, but something else must have happened day before yesterday when I used 100 grams of sodium chloride per liter of working developer to see if it would affect the grain from a particular developer of mine-- the Rodinal-like Metol developer in one of the articles. Strangely, it appeared that nothing visible happened. The result looked just like the previous test strip which had no NaCl. Both were from the same roll of the same subject, same exposure. I couldn't tell by close examination which has the chloride. I'm pretty sure the conditions in most developers are not favorable to bleaching either by chloride or bromide. I know it doesn't take much ferricyanide to have an effect on developer, and it's probable that the tiniest bit of ferricyanide added to the soup with the chloride would have had a major effect.

    It looks like the way to make POP is the old fashioned way. If you want the texture of current photo papers, I suppose you could bleach and wash some junked enlarging paper to use for the base. Clorox, of course, will remove emulsion in a jiffy.
     
  6. Photo Engineer

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    You are talking about film and we were talking about paper prints. It may be that any change is too small on the negative to see, or the iodide in the film emulsion and the high level of bromide may have inhibited the bleach reaction.

    Try using microdol on a paper print to develop it and you will probably find a decrease in speed for the same reason. The chloride is etching away the latent image in the toe.

    PE
     
  7. gainer

    gainer Subscriber

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    By the same token, I guess Microdol is not as effective on modern emulsions.

    I shall try the salt next time on a print. The concoction I have with salt added is not far from Microdol. Perhaps I need some more sulfite. I'll see. At my age about the only fun I can have is in the darkroom. Belay that. I have a great grand daughter who's only a few months old who already knows how to make me laugh.
     
  8. Jordan

    Jordan Member

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    So potassium ferricyanide plus sodium chloride plus hypo is a workable reducer? (Maybe the hypo isn't even necessary?)
     
  9. Photo Engineer

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    Jordan;

    The toe will bleach out faster than the shoulder and chloride is in no way as powerful as hypo. I didn't mean that. What you can end up with is a very high contrast image with no highlight detail if you do it on prints, and no shadow detail if you do it on negatives.

    Patrick;

    IDK why Microdol would not be as effective on modern emulsions. In a developer, the silver is dissolved and redeposited by physical development so this is an entirely different situation.

    PE
     
  10. gainer

    gainer Subscriber

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    I jumped to that conclusion when you said I did not see the expected effect of salt on film negatives in my Metol developer perhaps because of the iodide in modern emulsions along with the bromide. I think my developer is not that far from Microdol which is not so far from D-23 plus salt. I could be wrong. There's a first time for everything, as one of my teachers used to say, also tongue in cheek.
     
  11. dancqu

    dancqu Member

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    I wonder also if an image on paper bleached using
    ferricyanide/sodium chloride would have that POP look.

    According to Mr. Rudman's comments and expansion
    of the subject in the thread "Potassium Ferricyanide
    Questions", sodium chloride is entirely usable. From
    reading I'd go for P. Formulary's pure NaCl.

    What have you in mind for that after the bleach
    silver chloride image? A sunbath and ? Dan
     
  12. Photo Engineer

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    I repeat, it can be done but you can lose highlight detail in prints due to the blixing potential of ferricyanide-chloride. If the concentration is very very low, then it will affect some highlights and bleaching will be incomplete in shadows.

    If you wish to use it, use the purest form of NaCl to prevent stains or discoloration. Do not attempt it with ammonium chloride, as that is an even better silver halide solvent.

    PE