'Poitevin's Direct Positive Process'

Discussion in 'Alternative Processes' started by alexhill, Feb 27, 2011.

  1. alexhill

    alexhill Member

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    Edit: I forgot to mention this was on pre-srunk reeves bfk paper sized with glyoxal and gelatin.

    http://www.artic.edu/~fendsley/altProc_Poitevin.html
    Its a snow day here in maine, and i had the required chemicals around so I just gave the formula found here a go.
    Does anyone have a source for more information about the process described ? It appears to be leaving out the gelitine, as found in this version .

    After a 30 min exposure and a water development i have something of an image. My second attempt was with a stoffers step wedge and is found below

    Exact formula I used:
    1/4 inch cube of artist grade liquid watercolor paint
    5ml of sensitizing solution

    Sensitizing solution:
    5 grams ferric chloride
    1.5 citric acid
    50 ml water
    (remember to add acid to water! I forgot and got an awesome steam puff)

    [​IMG]
     
    Last edited by a moderator: Feb 27, 2011
  2. Vaughn

    Vaughn Member

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    The first link mentions the gelatin, but seems to forget it further down in the instructions. I do prefer Swan's improvements on the process.
     
  3. alexhill

    alexhill Member

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    By Swans process, do you mean the carbon print?
     
  4. holmburgers

    holmburgers Member

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    Be sure to read Luis Nadeau's "Direct Carbon Processes" or it's also covered "History of Carbon Processes" [sic].

    Cool! I just read about this, so it's neat to see.

    (edit: sorry, I just realized this was different that his carbon processes. I saw "direct" and got excited...)
     
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  5. Bob Carnie

    Bob Carnie Subscriber

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    Alex would you mind posting a jpeg of the original pos to see the difference??
     
  6. Vaughn

    Vaughn Member

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    Yes...sorry for the off-the-cuff remark. And I mis-understood what the process actually was -- mistaking "direct" for meaning no transfer.
     
  7. alexhill

    alexhill Member

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  8. alexhill

    alexhill Member

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    Sorry for the double post, but I don't want to start a new thread just to continue this one

    I realized that I could add A treatise on photography to my google bookshelf and read it. For connivence I typed out the relevant text below.

    I gave a detailed account of my experiments here . But the result leads me to suspect my sensitizer. I replaced the tartaric acid with citric acid because it was recommended over at alt photo in a comment.

    Does anyone have any suggestions?
     
  9. holmburgers

    holmburgers Member

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    Is it possible that the glyoxal in your subbing is migrating to your "image-bearing-gelatin-layer" (FLOABT) and rendering the whole thing insoluble? Does the old text mention a hardened subbing layer or just a plain piece of paper?

    Ok, with these tests....

    To try and remove as many variables as possible I tried two other experiments. The first was to run boiling water over some of the un-sensitized paper coated with pigmented gelatin. The gelatin dissolved rapidly leaving no stain. The second test was with a scrap of the sensitized paper that had not been exposed to light. That did not dissolve under boiling water leading me to conclude that my problem lies with the sensitizer.

    Were either of these test sheets subbed?

    Also, I noticed that you "... then mixed up a 5% solution of gelatin (7 grams to 150ml of water) and heated it to 140* f until the gelatin was melted. I took 15 ml of the melted gelatin and added a 1/4" watercolor pigment and mixed until blended."

    In carbon, it is recommended never to exceed 120°F, so that 140° stands out to me.

    Just some thoughts, I don't know if any are relevant or not.
     
  10. alexhill

    alexhill Member

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    This was the kind of response I was hoping for. I had seen gelatin heated to 140 for both making emulsions and subbing- so thats why I tried it at 140. I'll give the 120* a go.

    All of the tests were subbed with the gelatin and glyoxal. I'll also try using some un-subbed paper. I tend to use the subbed paper because it prevents the watercolor pigment from staining the paper. Not all pigments are staining, but enough of them are that it makes life easier to just sub everything and not worry about it.

    I'll post again when I have test results, most likely wont be for a week or so. My darkroom flooded :/
     
  11. holmburgers

    holmburgers Member

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    Wow, serious bummer. :sad:

    Good luck though, and I'm looking forward to the results.
     
  12. Hexavalent

    Hexavalent Subscriber

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    If you are hardening your subbing with an aldehyde (glyoxal,formalin, glut), it will off-gas. I'd be inclined to allow your subbed paper to 'breathe' for a few days before applying the actual 'imaging' layer.
     
  13. alexhill

    alexhill Member

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    The paper i used had been subbed anywhere from 2 weeks to two months ago.
     
  14. holmburgers

    holmburgers Member

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    Have you given in another go yet?