Bleaching a print.

Discussion in 'B&W: Film, Paper, Chemistry' started by kjsphoto, Jan 7, 2005.

  1. kjsphoto

    kjsphoto Subscriber

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    How do I bleach a print. What do I need to be able to do this?

    Thanks,

    Kev
     
  2. Juraj Kovacik

    Juraj Kovacik Subscriber

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    recepy from Whalley bromoil book

    Copper sulphate ... ... ... ... ... ... 1 oz.
    Potassium bromide ... ... ... ... ... 1 oz.
    Potassium bichromate ... ... ... ... 25 grains'
    Sulphuric acid (concentrated) ... 20 minims
    Water ... ... ... ... ... ... ... ... ... to 16 oz.

    I use it without Sulfuric acid

    Potasium bromide 100 g in 1 liter
    Cooper sulphate 100 g in 1 liter
    Pottasium bichromate 10g in 1 liter

    working solution 500 l water, 70 ml Potassium bromide, 70 ml cooper sulphate and 30 ml Potassium bichromate

    another recepy from Mayer bromoil manual

    This bleacher is the following :
    A. Copper sulphate ,...................................,...,,.... 20 g 1 oz.
    Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 ccm 5 oz.
    B. Potassium bromide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 g 1 oz.
    Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 ccm 5 oz.
    C. Potassium bichromate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 g * oz.
    Water . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 100 ccm 5 oz.

    For use, take :
    Stock Solution A ,,.....................,......,...,....... 45 ccm
    Stock Solution B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 ccm
    3 oz.
    3 oz.
    Stock Solution C ...................................... 15 ccm 1 oz.
    Hydrochloric acid, C. P. .......................... 1 ccm 20 minims
    Water ........................................................ 200 ccm 15 oz.
     
  3. rogueish

    rogueish Member

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  4. ann

    ann Subscriber

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    what type of bleaching technique? there is local bleaching ,global bleaching; bleaching for toning, etc. More information would be helpful in aiding you.

    Second Tim"s book.
     
  5. Andre R. de Avillez

    Andre R. de Avillez Member

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    For bleaching to lighten a print (whether locally or globally) I use a dilluted solution of Iodine tincture (the first aid stuff). I works very well, it's easy to buy, and pretty cheap too.

    It does not stain the prints or anything (just re fix the prints after bleaching and the iodine dissapears). In fact, fixer is so good at clearing up the iodine, that if you let some drop in the "bleach" you will ruin it (although it will look pretty cool as it ruins).

    Anyway, here's a link to the "recipee" I used last time (as you may have guessed, I just ruined the batch I was using and will make up another one):
    http://www.apug.org/forums/article.php?a=65

    hope this helps

    André
     
  6. hortense

    hortense Member

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    See Steve Anchell's, "The Darkroom Cookbook", 2nd edition, pp. 101-103 (you will find a very complete disertation on the subject as well formulas). This is a MOST worthwile book and should be in every large format photograpers library.
     
  7. Ole

    Ole Moderator Staff Member

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    A very simple bleach is 10 g potassium dichromate in one liter of water. Add about 15 gram potassium bromide, unless: it bleaching for toning, add 10 to 20 g of salt, Potassium bromide or potassium iodide to that liter of mix. If bleaching to clear highlights, fix in rapid fix afterwards.

    Toning looks slightly different depending on which halide you use. Fixing is difficult with iodide, and overly agressive with chloride. So it all depends...
     
  8. Ed Sukach

    Ed Sukach Member

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    What happened to/ about plain old pottasium ferricyanide? Seemed to work farily well to me.
     
  9. Ole

    Ole Moderator Staff Member

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    Replace Pot. dichromate with pot. ferri in the above recipe. Same difference.
     
  10. Wally H

    Wally H Member

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    I was told that potassium ferricyanide + acetic acid (stop bath) would produce cyanide gas. Will potassium dichromate also do this? (assuming the former is even true as I've never verified or tried it).
     
  11. kjsphoto

    kjsphoto Subscriber

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    What is the best way to buy the checmicals. Also I am not good at chemistry but I am learning and I like to make a liter of working solution at a time. I do not normally make the step before working I just make the working. Is this a bad way to mix chemicals?

    Thanks,

    Kev
     
  12. Andre R. de Avillez

    Andre R. de Avillez Member

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    I don't think that that's a bad way to mix the chemicals. Sometime I don't mix the concentrate either, I just mix the working solution. Can't think of a reason not to do it... anyone?
     
  13. Juraj Kovacik

    Juraj Kovacik Subscriber

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  14. Ole

    Ole Moderator Staff Member

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    Pot ferri will give off cyanide in a strong acid. If your stop bath was that strong, you would etch the emulsion right off the paper... I wouldn't worry.

    The cyanide would come from breakdown of the ferricyanide. So it cannot happen with dichromate.