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  1. #1

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    Developing B&W films to positive without second exposure

    Hi, I am asking if anyone here can guide me on developing B&W films to positive films without second exposure. I used to see some B&W films (Neopan 400 if I am not wrong) being developed as sepia looking positive before and was told that it can be done without having the need for a second exposure. But I am not sure of the chemical needed and the process.

    Thanks a lot for those that reply.

  2. #2
    holmburgers's Avatar
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    Sodium Sulfide.

    Here's a post explaining its use, from this thread.

    I think this is what you're referring to, right?
    If you are the big tree, we are the small axe

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    Thanks alot, I will read it up and try to understand.

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    My pleasure!

    Their is some good information after the post I linked to, explaining his procedure in more detail. Someone else can probably give a better explanation, but the sodium sulfide "fogs" every silver-halide that remains (just like light) and at the same time develops it to a lovely brown color.
    If you are the big tree, we are the small axe

  5. #5

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    sepia bw-slide step by step:
    1) developing
    2) stop
    3) sepia fogging developer 3min:
    Thiourea 5g
    NaOH 10g
    Water 1l
    4) bleach 3-5min in:
    Potassium dichromate 12g
    Sulfuric acid 10ml
    Water 1l
    5) clearing bath 2min:
    Sodium sulfite 30g
    Water 1l
    6) wash

  6. #6
    mrred's Avatar
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    Shouldn't step 3 be the last? You need 4 & 5 to be done before the fog.

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    Quote Originally Posted by mrred View Post
    Shouldn't step 3 be the last? You need 4 & 5 to be done before the fog.
    No, the Thiourea bonds with the undeveloped silver, not the converted silver. Now there is a Black and Sepia piece of film. The bleach does not effect the sepia portion but removes the silver. A very clean process.
    D-76 is a standard developer, although not one I use.
    Ansel Adams - The Negative

  8. #8
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    Doesn't it need to be fixed somewhere in that process?
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    Quote Originally Posted by Jeff Bannow View Post
    Doesn't it need to be fixed somewhere in that process?
    Ya, I also wonder why it doesn't need to fix or harden after an acid run. Won't emulsion be soft?

    Thanks to those who reply. I also found some solution online. It seems that the formula is quite the same as the one above except the process step is different, but I doubt there will be any difference since the bleach only remove processed silver by normal B&W developer (Correct me if I am wrong). Also, it seems that you can sub Sulphuric Acid with Sodium Bisulphate. Correct me if I am wrong, but powdered chemical are easier to find in smaller quantity than liquid. I can get 5kg of it from a local pool equipment supplier than taking the trouble to filter used car battery.

  10. #10

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    Quote Originally Posted by Jeff Bannow View Post
    Doesn't it need to be fixed somewhere in that process?
    fix isn't required in this process

    Quote Originally Posted by trexx View Post
    No, the Thiourea bonds with the undeveloped silver, not the converted silver. Now there is a Black and Sepia piece of film. The bleach does not effect the sepia portion but removes the silver. A very clean process.
    trexx, you right. really you can change sequence fogdev-bleach-clear-wash to bleach-clear-wash-fogdev with same result. but interesting that bleach as final step allow to process C41 color negative film as bw-slide and decrease density of orange mask. for process C41 film I'm recommended change bleach to more concentrate:
    Potassium dichromate 50g
    Sulfuric acid 30ml
    Water 1l
    process 5min

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