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  1. #1
    mikewhi's Avatar
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    RE: Need formula for Potassium Ferracyanide

    Hi:

    Memory going bad. I haven't used this for bleaching prints in a LONG time. Can someone remind me how this is mixed and used? I have the chemical powder in Kodak bottles. I know I used to mix it in with the fixer and bleach the entire print at once and I used it with cotton swabs and applied it locally on the print. I preferred to use a weak solution sl the bleaching came on slowly and could be arrested before it went too far.

    I also recall this comes packaged with Farmers Reducer, part A I think. Correct?

    Thanks in advance,

    -Mike

  2. #2
    Aggie's Avatar
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    for the bleaching I do, I learned it from Bruce Barnbaum. The Potassium Ferricynide should be mixed with water to the color of a nice yellow not a strong yellow but a medium one. I do not measure. Get your print wet first then work in good light. Bruce has some nice surgical hosing set up so that he can use a stream of water as he works. I use Japanese calligraphy brushes to apply the bleach. when it is nearing the bleaching in the particular spot that I want, i hurry and put it in a tray of fixer which stops it complete from bleaching further. Use the water stream to keep the bleach solution from flowing into portions of the print you won't want it to go. Slow is good. If you try to bleach too quickly or too much at once you will have a mess. Do little spots at a time and for a little time. Once it has been in the fix, you can rinse it well and rebleach. Oh and Bruce has a nice opaque plexiglass sheet he has at an angle in his developing sink so that when the print is wet he can adhere it to it. It keeps the print at about eye level so that you can get closer to watch the bleaching action. The bigger the brush the bigger the area you can work with.

    If blonde speak needs translation ask what I messed up explaining.

  3. #3
    ann
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    We have used a 10 % solution of "ferri" with about 5ml of weak fixer for local bleaching.
    There are a variety of formula for global bleaching; are you looking to re-developer after or use of a general lighting?

    One standard bleach formula would be :
    ferri 10 grams
    potassium bromide 5 grams
    water for 1 liter

  4. #4

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    I use the process described by Aggie and I'm satisfied with it. One caution, If you use a brush to apply the bleach solution, be sure it doesn't have a metal ferrule.

    Sam
    Its all about the image, not the process.

  5. #5

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    There is a book for you to find that will give you an idea about the potential for disaster when using Potassium Ferricyanide. It is called, Overexposure, Health Hazards in Photography. You will see that mixing any acid with Potassium Ferricyanide produces cyanide gas, not really a good thing for a long career in photography, albeit a small concentration. You do not need to use fixer, it is an old school way of getting the bleach to act faster (it becomes an accelerant). Be sure before you put your print back in fix after bleaching that you rinse it very thoroughly with water or the residual will suddenly act up again for the same reason. I agree with Aggie fully too, you need to start slowly and patiently, you can always bleach some more. Of course, wear gloves and have ventilation.
    Take a gander at that book too though, it's a good thing to have as a reference in any photo library...
    Good luck, Ray
    Do not question what you have not done, question what you will not try.

  6. #6
    mikewhi's Avatar
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    Good point, 'happysnapper'. This stuff is poisonous, and I think the bottles I have have the 'skull and crossed bones' on it, even. DO NOT for any reason get this stuff in you. As I understand it, the stuff basically suffocates you by inhibiting blood from carrying oxygen, or something like that. I do recall reading that the guy who made\discovered this stuff actully killed himself with it.

    I have used it in the past, but I didn't go so far as to wear masks or heavy fans in the area etc. I did keep my fingers out of the stuff using tongs all the time.

    It is great tool, just know you're dealing with a poison and take reasonable precautions. Plenty of people have used without killing themselves, and there is no reason you can't be one of them!

    -Mike

  7. #7
    Aggie's Avatar
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    precautions are one thing, paranoia is another. The cyanide gases given off from the very small amount you would be working with is far less than the chlorine gas given off from a swimming pool. Maybe we should not go swimming in swimming pools.

  8. #8
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    From the Darkroom Cookbook, by Stephen G. Anchell:
    You can use Farmers reducer or Kodak R-4a.
    "Use a strong solution of Farmers or R-4a. For print reduction with R-4a, mix 1 part A, 1 part B and 10 to 15 parts water depending on desired rate of reduction. One methods recommends (Farmers)1 part A to 2 parts B without adding water. If you feel the action is too slow, add a little more solution A. An alternative to Farmers reducer is medicinal iodine tincture. remove the iodine by immersing print in hypo just as you would with Farmers; fix and wash. NOTE" Always use a non-hardening fixer for any after process such as reduction, intensification, toning, etc."
    What is in the book is more detailed of course, but that should help prod your memory lapse.
    As to safety, ALL photographic chems are toxic to one degree or another and should be handled with care and a little common sense. Good ventilation is recommended. Oh, and don't be sipping the brew even it is Farmers brew...

  9. #9

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    Quote Originally Posted by Aggie
    precautions are one thing, paranoia is another. The cyanide gases given off from the very small amount you would be working with is far less than the chlorine gas given off from a swimming pool. Maybe we should not go swimming in swimming pools.
    Aggie,
    It is always better to take precautions don't you think? The last I heard, they didn't use chlorine gas to execute people in the gas chamber either. As you bleach, I do believe that you would have your face right down on your print in order to see what you are doing. I don't suppose you have a scale for the proximity effect. Read the book I suggested.
    And stay out of the pool...
    Last edited by Sean; 07-22-2004 at 05:35 PM. Click to view previous post history.
    Do not question what you have not done, question what you will not try.

  10. #10
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    Quote Originally Posted by happysnapper
    Aggie,
    It is always better to take precautions don't you think? The last I heard, they didn't use chlorine gas to execute people in the gas chamber either. As you bleach, I do believe that you would have your face right down on your print in order to see what you are doing. I don't suppose you have a scale for the proximity effect. Read the book I suggested.
    And stay out of the pool...
    Aggie is right on here. It takes a REALLY strong concentrated acid to cause potassium ferricyanide to release any cyanide gas. The chemical bonds of the iron and cyanide are very strong. Diluted stop bath won't do it. Acidic fixer won't do it. The book you mentioned by Susan Shaw is generally regarded by anyone with any chemistry knowledge as an alarmist, scientifically dubious cut and paste job that makes some wild extrapolations from a pile of MSDS information. Hysteria sells well in the USA.

    The short answer, yes, be careful with any chemical. Don't dip your hands in any solution ungloved. Wear a mask when mixing up dry chemicals. Ventilate your darkroom. Don't eat and drink in the darkroom. But you can relax about the potassium ferricyanide. (potassium cyanide is another matter altogether) Heck, that is the main ingredient in cyanotypes, which is considered safe enough for kindergartners to slop around and make sun prints.
    Last edited by Sean; 07-22-2004 at 05:35 PM. Click to view previous post history.

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