'Poitevin's Direct Positive Process'

alexhill · Feb 27, 2011

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

Dead Link Removed
Its a snow day here in maine, and i had the required chemicals around so I just gave the formula found Dead Link Removed 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)

Vaughn · Feb 27, 2011

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.

alexhill · Mar 1, 2011

By Swans process, do you mean the carbon print?

holmburgers · Mar 1, 2011

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...)

Bob Carnie · Mar 1, 2011

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

Vaughn · Mar 1, 2011

alexhill said:
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.

alexhill · Mar 1, 2011

This is the exciting positive I used http://3.bp.blogspot.com/_2IigzeTmd.../s1600/MESNEY_Printing_Exposure_Scale_1.1.jpg . Ill be descending down to the darkroom again today and tomorrow to see if I can get a better result.

alexhill · Mar 10, 2011

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?

holmburgers · Mar 10, 2011

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.

alexhill · Mar 10, 2011

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 :/

holmburgers · Mar 11, 2011

alexhill said:
My darkroom flooded :/

Wow, serious bummer.

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

Hexavalent · Mar 11, 2011

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.

alexhill · Mar 14, 2011

Hexavalent said:
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.

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

holmburgers · Apr 11, 2011

Have you given in another go yet?

'Poitevin's Direct Positive Process'

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