Potassium ferricynide question.

Discussion in 'B&W: Film, Paper, Chemistry' started by mario Ag+, Nov 23, 2006.

  1. mario Ag+

    mario Ag+ Member

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    Hi all,
    Is it posible to use Pot Ferricynide on it's own (without Pot bromide ) as a print bleach. I'm thinking of making a 10% solution first and highly diluting it to give me more control. Will this work? or is Pot Bromide esential in print bleach.
    Mario.
     
  2. Ole

    Ole Moderator Staff Member Moderator

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    The bromide is only necessary if you are going to redevelop (i.e. tone) the print. Potassium ferricyanide will bleach on its own, but you should add either a halide (chloride, bromide or iodide) or thiosulfate (fixer) to take care of the released silver.
     
  3. Les McLean

    Les McLean Subscriber

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    If you are wishing to bleach the print to lighten highlights add a small amount of hypo crystals or ordinary fixer to the ferri solution. Ferri mixed with bromide is used to bleach the image and redevelope in toning solution when sepia toning.
     
  4. KenM

    KenM Member

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    Yes, you can bleach just using Pot-F. However, it's very important that you return the print to the fix to completely neutralize the bleach. I don't like adding fix to the bleach, since it drastically shortens the life of the bleach (yeah, yeah, it's cheap, I know).

    Also, keep in mind that some papers (Ilford, to name one) may not bleach very easily unless you add some fix to the bleach to help things along. Forte papers bleach very easily with just bleach....
     
  5. mario Ag+

    mario Ag+ Member

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    Thank you all for your replies.
    Mario.
     
  6. dancqu

    dancqu Member

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    P. ferricyanide oxidizes elemental silver. The oxidized
    silver will complex with fixer and be removed. If bromide
    is present the oxidized silver is converted on site into
    silver bromide. So with bromide present the image is
    left as silver bromide.

    Now what would happen to that remaining image if it
    were exposed to light and put through a print developer.
    Anybody tried that? And to make it more interesting,
    if it were a chloro-bromide paper at start,
    at end it is a bromide only. Dan
     
  7. tim rudman

    tim rudman Member

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    If you fix after ferri-bromide (or mix of halides) the silver halides will be removed. If you don't fix, they can be redeveloped. I use this a lot and we usually have a whole day of 'bleach and redevelopment games' on my longer workshops. It's not only great fun but very useful and can be creative.
    It gives you the chance to bring a print back in a warmer or colder tone, higher or lower contrast or in lith developer as wel as in a variety of toners.
    Yes, changing the halides does change the results.
    Tim
     
  8. dancqu

    dancqu Member

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    I'd suppose the halide or mix thereof would affect
    the amount of post ferricyanide exposure needed?

    After rehalogenation and the correct amount of
    re-exposure does a same print developer
    reproduce same results? Dan
     
  9. tim rudman

    tim rudman Member

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    You are right that different halides might require different exposures - but the exposure is all done at the first exposure. There is no need to re-expose after bleaching. The bleaching and redevelopment are all done in normal room light, not safe light.
    The idea is as follows:
    1) You buy a sheet (packet/box etc) of paper coated with a (light sensitive) silver halide all over.
    2) You expose through a neg to produce a latent (invisible) image
    3) You develop the paper to change the silver halide THAT HAS BEEN EXPOSED TO LIGHT into metallic (visible) silver - the image.
    4) at this point, you can't turn on the lights as all the original (non image) light-sensitive silver halide(s) is still present all over the paper and would react to light
    5) You fix the print. This removes all the unexposed silver halide, leaving only the metalic silver of the image. White areas have no silver (halide) left at all if you fix fully. You can now put lights on.
    6) you now wash to remove fixer AND silver/fixer complexes (argentothiosulphates)

    Now you have a halide-free print with an image made of silver metal, which (unlike the silver halide) is visible.

    If you bleach this silver image in a Pot. Ferri/halide bleach (e.g. a sepia kit bleach) you convert this metallic silver back into a silver halide.

    This is where we began - ALMOST
    But the silver halide we now have is
    a) only where the image was - not all over the paper, and
    b) is less light sensitive and can be handled in normal room light reasonably well.

    SO - we can go back to the beginning and develop again. The image is there so no further exposure is needed.
    BUT - this 2nd development can be in a different developer - e.g. cold tone, warm tone, Lith, high contrast, low contrast etc etc etc, ... so you see how useful and powerful this can be ...

    but there's more ;-) ...

    - The bleach can be full or partial (leaving part of the image unaffected)
    - The bleach can contain different halides, or mixes of halides
    - The 2nd development can be complete
    - Or it can be partial (different colours from partly developed grains - especially good with Lith dev)

    If the 2nd dev is partial the print will become lighter in the 2nd fix (you must re-fix if 2nd dev incomplete as silver halides still exist that haven't been developed back to silver metal and these are unstable in light eventually)
    SO - you may ned to compensate for this by making the original print a bit darker.

    The point of all this is that
    - you can now not only have all grades in one box of VC papers, you can have many different paper types as well! How cool is that!?
    - You can also make '2nd pass' Lith prints that are quite different.
    - You can also change the way a certain paper responds to selenium (for example) toner - WOW ;-))
    and - as they say - so much more ;-)

    That is the basis of part of my 'Day at the Bleach' worshop day - or if you prefer .. 'Once more into the Bleach dear friends'
    Tim
     
  10. AgCl4ever

    AgCl4ever Member

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  11. dancqu

    dancqu Member

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    I've been digging into the chemistry of the process.
    I've not found anything of which I'm sure Mr. Rudman is
    not already well acquainted. As I previously mentioned, the
    silver is oxidized by the ferricyanide. Silver + ferricyanide =
    silver ferrocyanide.

    The ferrocyanide is insoluble so image integrity should
    be maintained through a P. F. treatment. Assuming your
    intention is to sepia tone, a P. F. minus bromide treatment
    may suffice. That is no bromide during or after treatment.
    Due to the extreme insolubility of silver sulfide it stands
    to reason that the silver will convert.

    At a minimum an interesting experiment would be a post
    rather than a during bromide treatment.

    You asked " is Pot Bromide essential ... ?" If so, I'd add
    when is it essential, during, after, either? Dan
     
  12. tim rudman

    tim rudman Member

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    I'm not sure I quite understand your question Dan.
    Do you mean bleaching with plain Pot. Ferri (no bromide), then sepia toning, then adding bromide after toning? Why would you want to do this? Perhaps I missed the point?
    Tim
     
  13. Ole

    Ole Moderator Staff Member Moderator

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    Some of the "other metal" toners work without halides - like the blue iron toner.

    Adding halide after toning will probably have no effect at all. I say "probably" because I haven't tried it, although a strong salt (sodium chloride) solution is used as a clearing bath with the Colorvir toning kit (iron, zink and titanium toners).
     
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  15. Stoo Batchelor

    Stoo Batchelor Member

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    Hi

    This thread has horrified me.

    If I was to answer Marios question above, I would have said; 'Yes, of course it is Mario'

    Now reading through this thread, all the past prints that I have made are likely to self disruct over time. Could some one please tell me this is not going to happen.

    I print on Ilford Mg4 FB and wash and fix as per normal.
    The print is washed for 1 hr.
    The print is then slid in to a tray of 1ltr of water and 10ml of Ferri-stock(10gms ferri/100ml water, as per Les McLeans book)
    The tray and print is agitated sporadically throughout its 10 mins soak.
    The print is washed for 2 mins
    The print then enters a tray of sepia(tetenal non vario) for 10 mins
    The print is washed for 5 mins
    The print then enters a tray of selenium of either 1-9 or 1-4 for the desired effect.
    The print is washed for a further 30-45 mins
    The print then enters atray of 2x Alcha-Seltzer/1ltr R.O water for 1 min before the usual drying procedure.

    This is a routine that I have been using for some time now and I have not noticed any degradation of the final print over time. They all look as crisp as the day they were printed.
    Should I be adding some fix to my tray of weak ferri, and if so, how much?

    I thank you in early anticipation, and also appologise to Mario for asking a question on his thread.

    Kind Regards

    Stoo
     
  16. dancqu

    dancqu Member

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    I've not been trying to make a point. I've got some
    potassium ferricyanide on my list of to-buy chemicals
    when next I order from P. Formulary. I've taken the
    OP's question as an opportunity to investigate
    the matter.

    At least at first glance it would seem that bromide
    is not needed if a sulfide toner is to follow the bleach.
    Ole mentions "other metal" toners which work with
    out any halide.

    With the usual lights-on way of P. F. processing the
    re-exposure I mentioned is included. We know that the
    halides of silver are light sensitive. Now, what if the P. F.
    processing is done under, say, a red safelight? What then
    if the re-halogenated print is again put through a usual print
    developer? My guess, the print would not reappear. Would
    not because of it's P. F. processing under a red safelight.

    Besides silver ferrocyanide and the halides when
    present, I dare say several other compounds of silver
    could be generated with the appropriate chemical; that
    during or after a P. F. treatment. That you've mentioned
    at least with the halides or a mix thereof.

    But for some of those "Cool" moves that might be made
    re-exposure is necessary. So, the light sensitivity of what
    ever compound of silver results must be considered. The
    halides are sensitive and some what the soluble nitrate.
    Others I couldn't say. Dan
     
  17. gainer

    gainer Subscriber

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    Not unless you want to lose the image. Fix + ferri = Farmer's Reducer. The image will not resurrect.

    Bromide is not the only halide. Non-iodized table salt will do. Canning salt is such. You get a silver chloride image which responds to sulfide for toning or which may be redeveloped in a staining developer for other purposes. Light is necessary for the latter. Sulfide will turn unexposed film or paper brown.
     
  18. Stoo Batchelor

    Stoo Batchelor Member

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    Hi gainer

    Thanks for the reply.

    Sorry to dig deeper, and if i sound a bit dense here, but i want to get this straight. From what you are saying, I assume that all is o.k with my toning routine? As I am only slightly bleaching out the highlights with the ferri, as soon as I enter the print in to the sepia toner, any un-developed silver is re-developed, providing that I use a sulphide toner.

    Just one other question, if I may?; Would a Sepia toner made out of Thiourea do the same job as the sulphide based sepia toner, i.e; re-develop any un-developed silver?

    Kind regards

    Stoo
     
  19. tim rudman

    tim rudman Member

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    Perhaps I can add my comments here too Stoo.
    'Gainer' is right about fixer + ferri = Farmer's reducer, which is non reversible. This is also important as you must take care to properly remove fixer from the paper too, before putting it into your ferri/halide bleach.

    "As I am only slightly bleaching out the highlights with the ferri, as soon as I enter the print in to the sepia toner, any un-developed silver is re-developed, providing that I use a sulphide toner"

    Correct - provided that you tone to completion.

    "Would a Sepia toner made out of Thiourea do the same job as the sulphide based sepia toner, i.e; re-develop any un-developed silver?"

    Yes, this is correct. Plus you have the advatages of no bad smell and you can pick from a range of colours from thiourea, by altering the hydroxide amount that is added to it. In kits this usually comes as a 3rd bottle of 'additive'.
    There are other ways you can alter the outcome too by adding a different halide (eg kosher salt) to the bleach, by adding a little B&W developer, by putting in toner before bleaching etc etc.

    Re halides - you can use bromide or chloride as previously stated, or a mix. Iodide is also usable but much trickier. If interested, there is a write up on this in my toning book under FSA toner (too long to retype here!)
    Tim
     
  20. Stoo Batchelor

    Stoo Batchelor Member

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    Phew, I can rest at night now!

    Tim,

    Thanks for taking the time out to answer my Question. I have actually ordered the raw chemicals now to make my own Thiourea based toner, so look forward to playing games and experimenting with some old prints.

    I am the owner of a copy of your toning book, its the bible of toning. I have ballsed up many a fine print while reading it!:tongue: I will read with interest the pages you have suggested.

    Thanks again, glad your there.

    Kind Regards

    Stoo
     
  21. phritz phantom

    phritz phantom Member

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    so, i finally found out that "hypo" does not mean "hypo clearing agent", but "sodium thiosulfate".
    i was wondering for a long time, why some people mix bleach with fixer and others with hypo. thanks a lot for clearing that up.

    but....
    all the fixers i use don't contain "sodium thiosulfate". they contain "ammonium thiosulfate". is there a difference between those two chemicals when mixing it with potassium ferricyanide? or can i keep using the amm. thios. fixers?
     
  22. gainer

    gainer Subscriber

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    I would be a little leary about Kosher salt for photographic use. It is my understanding that Kosher means approved and blessed by a Rabbi for human consumption in accordance with certain principles that do not necessarily preclude the presence of iododes or other naturally occurring substances, so long as they are not harmful to humans. I'm pretty sure a thorough chemical analysis is not necessary, though I do not know the actual rules. The Law is much older than the chemistry. A better choice would be canning salt IMO.
     
  23. fschifano

    fschifano Member

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    Correct. Some brands of Kosher salt have something called "yellow prussiate of soda" included to prevent the salt from caking up. Other brands are nothing but pure sodium chloride. If you check the labels, it should tell you.
     
  24. Ole

    Ole Moderator Staff Member Moderator

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    Isn't that sodium ferrocyanate? If so, that's exactly what you don't want to mix with potassium ferricyanate!
     
  25. tim rudman

    tim rudman Member

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    Amm thiosulphate is 'rapid fixer'. It works fine with bleach too - but you will find that the ferri activity is short lasting (yellow colour goes too) and the mix needs topping up with PF as you go along.
    Tim
     
  26. tim rudman

    tim rudman Member

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    Thank you for that. I was under the impression that it was without the iodide that was added to normal table salt in the US.
    Good to know these things ;-)