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  1. #1

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    B&W Reversal bleach recipes

    I haven't done reversal processing on B&W film for several years. I always used Kodak's system cleaner as my bleach since after reading the label & checking the MSDS it seemed exactly the same as a normal acid/dichromate bleach.

    It worked great...and I didn't have to mix up my own chemicals and worry as much about spilling/dropping nasty chemicals on myself.

    But now I can't get the same cleaner.

    Actually buying a reversal kit would work....but it was always so convenient to just run out to the store and buy the System Cleaner & use my regular developers, etc .......besides, it's just more fun to mix stuff up myself.

    Has anyone tried the new non-toxic tank/tray cleaners as a reversal bleach?

    I read online that Edwal's cleaner might make the silver soluble in a sodium sulfite solution. Anybody know about this?

  2. #2
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    sorry, mine is toxic

    I use a chrome bleach - the yellow/orange one; but I reuse it many times untiil it is green, by which time it is apparently not as toxic, then it goes to the HHW drop off along with exhasted fixer, etc. If it comes out of the tank green , I mix up a new batch, and then pour it in again before I rinse and pour in the weak sulfite clearing bath.

    There is a one time option permanganate bleach as well, but the purple stuff stains the sink and everything like nothing else, and it is wash, wash, wash to get rid of the stain on the film.

  3. #3

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    yup..that's what I used..the chrome bleach

    the sodium sulfite wash after the bleach step turns the solution green also...and makes it less toxic IIRC

    I may try permanganate, but it would be interesting to try something new

  4. #4

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    There are lots of web pages on bleach out there. I have a couple described on my site (see link below). The yellow-orange colour in dichromate bleach is characteristic of chromium(VI). When you mix it with sodium sulfite, it is reduced to chromium(III) (I think -- might be II) which is green, less toxic and not active as a bleach. This is the reaction that occurs in the clearing bath after bleaching.

    Permanganate bleaches are stronger oxidants, which makes them more dangerous in contact with flammable materials, but they are not carcinogenic (unlike dichromate bleaches). Permanganate bleaches have to be mixed fresh before each use. A metabisulfite clearing bath after the bleach step gets rid of the murky brown stain (which I believe is from manganese dioxide). The cleared solution is sometimes faint pink in colour (the colour of manganese(II)).

    Permanganate bleaches tend to soften the emulsion, while dichromate bleaches harden it. This can make it hard to handle film that has been bleached in permanganate. Apparently, keeping the temperature slightly cool (~18C) and absolutely constant helps in this regard.

    I agree with you that tray cleaner is (was?) a particularly convenient source of dichromate bleach. You can still buy potassium dichromate and some sulfuric acid or sodium bisulfate and mix your own. Use extreme caution when mixing bleaches -- they are more corrosive, more toxic, and far more reactive than standard B&W chemicals.

  5. #5

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    thanks!

    so sodium bisulfate can be used instead of sulfuric acid with the dichromate?

    I noticed one supplier sells potassium dichromate as a 2% solution...I don't remember the strength needed for a bleach, but if it means I handle a toxic chemical less it seems good to me

  6. #6

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    really nice information on your blog

    so the second dev is just thiourea and sodium carbonate?

  7. #7

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    Sodium bisulfate (note -- not bisulfite) produces acidic solutions that are equivalent to an equal mixture of sodium sulfate and sulfuric acid. I've used it with good success. I do use thiourea and carbonate as a second dev to produce sepia positives. No light re-exposure is required in that case.

  8. #8

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    Well, I just HAD to try it....

    since I always had success with Kodak's system cleaner as my reversal bleach...and since somebody somewhere on the internet said they thought maybe Edwal's Tank & Tray cleaner would work...I tried it

    and...I ended up with slightly odd negatives

    when I looked at the film before the re-exposure it seemed as if maybe something was happening, but I think all the Edwal's did was dissolve some of the unexposed silver & left the developed image alone

    sort of the opposite of what I wanted

    I didn't really expect it to work anyway, but I would have been happy with a surprise success

  9. #9

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    I'm puzzled because I'm wondering why there are peolpe that continue to use the dichro bleach while there's a much safer alternative that works equally, if not better.

    Mr. Wosnick has pretty said it and his site is rich in content and beautiful photos.

  10. #10

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    http://potency.berkeley.edu/chempage...%20SODIUM.html for the dichromate
    http://potency.lbl.gov/chempages/THIOUREA.html for the thiourea

    In these pages look for the LD50.



 

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