[Alt-photo] Troubles with Calotypes, James' "Contemporary" Method
nirpat89 at yahoo.com
Fri Jan 12 11:26:37 UTC 2018
If the paper is buffered, the first step of silver nitrate application would result into silver carbonate formation (assuming the buffering agent is calcium carbonate.) Then the question is how much does the potassium iodide play a role subsequently. Depending on the equilibrium kinetics of carbonate vs iodide, one might be exposing not silver iodide but predominantly silver carbonate. Buffered paper can give a decent salted paper image without the use of any salt at all:
Acidification with acids that give insoluble or somewhat insoluble calcium salts such as calcium oxalate (from oxalic acid) or calcium citrate (citric acid) will react with silver nitrate as well to give silver oxalate, citrate respectively - once again complicating the subsequent salting step. In that respect, sulfamic acid might be a better option as calcium sulfamate is water soluble that can be washed out from the paper, leaving bare paper. I have also found, not unlike Ned's experience, that sulfamic acid treatment makes the paper very absorbing and porous (some of the gelatin sizing leaches out at low pH, isoelectric point of gelatin being somewhere around pH of 5.)
From: Ned Lewis via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
To: alt-photo-process-list at lists.altphotolist.org
Sent: Thursday, January 11, 2018 9:00 PM
Subject: Re: [Alt-photo] Troubles with Calotypes, James' "Contemporary" Method
In my google books "snippet view" some pages were not displayed and I
missed that the development was by brushing on the developer. 1:1 ANS toann
galic makes more sense for that. If you try that, be *very* gentle with a
cotton swab or soft brush, not rubbing the paper at all.
People have experienced mixed luck with Canson Marker. It did not work for
me with Geenlaw's process unless I acidified it, and even then the paper
did not keep well after iodizing. Something changed a couple years ago,
but there may still be some "good" pads around.
I acidified it by soaking for 1/2 hour in a mixture of 1 part white
distilled vinegar to 2 parts distilled water. Then I washed for an hour or
so and dried.
I know others have used citric acid. Maybe someone can chime in about that.
For salt prints, I've acidified papers using 2% citric acid and also
sulfamic acid. When I used 10% sulfamic acid ( see thread here at photrio
), I found that it damaged the paper sizing and in doing so brought out
screen markings, at least on the two or three kinds of paper I tried. 2%
sulfamic acid worked better, but these days I try to find papers that work
without doing more than adding a little citric acid to the salting solution.
Have fun and good luck!
On Wed, Jan 10, 2018 at 3:08 PM, J. Jason Lazarus via
Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
> Thanks to all of you who have chimed in - I greatly appreciate the help.
> Ned -
> James mixes in both Talbot's original method with this Contemporary
> approach often, making it a bit hard to follow along in the text without
> reading and re-reading the entire process. On page 73, he's referring to
> Talbot's original method that sensitized with gallo-nitrate and not
> aceto-nitrate. Skip a couple paragraphs and he lists the "contemporary"
> version of sensitizing with aceto-nitrate.
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