The basic process is simple enough. All one needs do is to dissolve the
basic ingredients, Ferric Ammonium Citrate, Tartaric Acid, and Silver
Nitrate in water, coat it on paper, dry, and expose. "Development" is
equally simple: wash in water for a minute and fix in a weak solution
of sodium thiosulfate. Unfortunately, like almost any other
photographic process, doing it is simple, while doing it well is
another matter. Certainly those of us who have seen lackluster platinum
prints can attest to that.
One of the difficulties I've encountered is paper choice. Some papers
just don't work well with Vandyke. Cranes Kid Finish works well, while
Cranes Resume does not.
The biggest problem that no one else seems to have noticed, however, is
the way the solution ages, along with the precipitation of the silver
in the solution, affects the image. After intitial testings, I've found
these differences between freshly mixed Vandyke solution and ones
several day old:
>From freshly mixed solutions:
1/ The printed out image appears more yellow-orange, where the one from
not-freshly mixed solution darker and less lively.
2/ During the initial rinse, the color is a richer, more chocolaty
brown compared to the more ochre brown from the older solution.
3/ After it's dried, the color turns to a deeper, more lively, and
cooler brown, with a longer tonal range, with steps 2 to 16 on the 21
step-tablet visible. The print from the older solution shows only steps
3 through 14, and in a lighter, less intense warmer brown.
The tests were made on Crane's Kid finish Ecruwhite, exposed and
processed at the same time.
My guess is that the differences are caused by the silver precipitating
out of the solution. Less silver, less dark.
Problem is, silver sometimes precipitate as white particles, and
sometimes dark particles. My hunch (lack of chemistry background may be
showing here) tells me that the white is undissolved silver, that can
be dissolved, according to Dick Sullivan, by adding more tartaric acid
to the mix. The black particles are obviously metallic silver, which is
best filtered out before use. Am I right?
If my hunches are correct, then the question is if there is some way to
prevent the precipitation from happening - to keep all the silver in
solution. For the time being, I'm going to keep some old stock and use
it when I need a shorter scaled, warmer solution. The rest of the time
I'm stocking the ingredients in separate bottles, and mix them only on
the day of use.
Sorry about the length of this message. Hopefully it's not going over
the same grounds as available in the archives.
Sam</bigger></fontfamily>
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Sam Wang e-mail: stwang@clemson.edu
Art Dept - Clemson University voice: 864/656-3924
Lee Hall, Clemson, SC 29634 FAX: 864/656-7523
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