Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,854   Posts: 1,582,921   Online: 990
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 14
  1. #1

    Join Date
    May 2010
    Location
    New Hampshire
    Shooter
    4x5 Format
    Posts
    177

    'Poitevin's Direct Positive Process'

    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)

    Last edited by alexhill; 02-27-2011 at 05:41 PM. Click to view previous post history.

  2. #2
    Vaughn's Avatar
    Join Date
    Dec 2006
    Location
    Humboldt Co.
    Shooter
    8x10 Format
    Posts
    4,755
    Images
    40
    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.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  3. #3

    Join Date
    May 2010
    Location
    New Hampshire
    Shooter
    4x5 Format
    Posts
    177
    By Swans process, do you mean the carbon print?

  4. #4
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    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...)
    Last edited by holmburgers; 03-01-2011 at 01:30 PM. Click to view previous post history.
    If you are the big tree, we are the small axe

  5. #5
    Bob Carnie's Avatar
    Join Date
    Apr 2004
    Location
    Toronto-Ontario
    Shooter
    Med. Format RF
    Posts
    4,706
    Images
    14
    Alex would you mind posting a jpeg of the original pos to see the difference??

  6. #6
    Vaughn's Avatar
    Join Date
    Dec 2006
    Location
    Humboldt Co.
    Shooter
    8x10 Format
    Posts
    4,755
    Images
    40
    Quote Originally Posted by alexhill View Post
    By Swans process, do you mean the carbon print?
    Yes...sorry for the off-the-cuff remark. And I mis-understood what the process actually was -- mistaking "direct" for meaning no transfer.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  7. #7

    Join Date
    May 2010
    Location
    New Hampshire
    Shooter
    4x5 Format
    Posts
    177
    This is the exciting positive I used http://3.bp.blogspot.com/_2IigzeTmdw..._Scale_1.1.jpg . Ill be descending down to the darkroom again today and tomorrow to see if I can get a better result.

  8. #8

    Join Date
    May 2010
    Location
    New Hampshire
    Shooter
    4x5 Format
    Posts
    177
    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.

    Printing with Ferric Salts
    Poitevin's Process with Ferric Chloride and Tartaric Acid

    In Poitevin's process another property of a ferric salt is brought to bear, viz., the fact taht it makes gelatine insoluble. A 6 per cent. solution of gelatine in water is prepared, with which is mixed any suitable pigment. Paper is floated on it whilst still warm. The paper now presents a uniformly coloured surface. To sensitise the paper it is immersed in a solution of
    Ferric Chloride ... 10 parts
    Tartaric acid .... 3 parts
    Water.................100 parts

    and after drying in the dark it is ready for exposure. When exposed to light, the gelatine, which is now insoluble, becomes soluble in hot water. If, therefore, the paper be exposed beneath a positive (reversed as regards right and left), an image may be developed by simple immersion in hot water. The parts which are insoluble remain next the paper, hence a perfect image may be developed with care. The student should compare this process with the autotype process (p.162), and not the comparative advantages and disadvantages of the two. it seems to the writer that there is a possibility of a great future development of this process.
    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. #9
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    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.
    If you are the big tree, we are the small axe

  10. #10

    Join Date
    May 2010
    Location
    New Hampshire
    Shooter
    4x5 Format
    Posts
    177
    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 :/

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin