From: Alan Greene (hobbyhorsedada@hotmail.com)
Date: 12/10/02-10:59:47 PM Z
Mike,
I'm no chemist, but my gut feeling is that potassium citrate and sodium
citrate are going to be interchangeable, since you are looking to form
silver citrate on salted paper, rather than potassium nitrate or sodium
nitrate (a.k.a. "salt peter"). If you already have sodium citrate, or find
that it is significantly cheaper than potassium citrate, try salting nine
sheets of paper substituting sodium citrate for potassium citrate in the
following way (keeping the salt level the same in all cases and noting the
changes in pencil on the backside margins of the paper): salt three sheets
in which the stated citrate level is cut in half; then add enough citrate to
match the stated level 1:1 and salt three more sheets; and finally, add
enough citrate to double the stated citrate level and salt the last three
sheets. Using the same negative, make a print from each of the three citrate
levels. Repeat this two more times with two other negatives of of similar
contrast levels and examine all of the results. Assuming that a consistant
citrate level yields the better print in all three cases, this is the level
you should use. Or you can fine tune it from there--changing both the
citrate and salt levels to match different negative contrasts, since neither
the citrate nor salt levels as published should be considered as absolutely
fixed. Different papers and negatives call for varying the stated amounts.
Still, if you're really stuck on using potassium citrate, Bernard Jones,
Encyclopedia of Photography (1911 ed.--definitely not contemporary, but
nonetheless a reliable standby) gives a simple way to make potassium
citrate, which I will attempt to paraphrase as follows: to make 480 grains
of potassium citrate, dissolve 295 grains of citric acid in 2 ounces of hot
[distilled] water; then gradually add 290 grains of potassium carbonate, or
enough to make the solution neutral to litmus paper after heating; filter
the solution [no doubt removing the precipitate salt peter] and then add
enough [distilled] water to make four fluid ounces total. This represents a
twenty-five per cent solution.
Hope this helps,
Alan Greene
>From: Michael Healy <mjhealy@kcnet.com>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: alt-photo-process-l@sask.usask.ca
>Subject: Potassium Citrate
>Date: Sun, 08 Dec 2002 21:27:25 -0700
>
>Mr. Science here wants to try salt prints. But Mr. Science knows only a
>little more about chemicals than the cat. Wings and prayers are what we've
>got going for us. So the formula calls for potassium citrate. Mr. Science
>here wouldn't know potassium citrate if it knocked on his door and bit him
>in the ass. The only place we're even finding the stuff is at
>Photographer's
>Formulary, which frankly is 25-40% more expensive item by item than, e.g.,
>B&S. But B&S doesn't seel pot. citrate. In fact, nobody seems to, apart
>from
>the vitamin supplement people.
>
>So what the hell IS potassium citrate? Is this the same thing as the
>vitamin
>supplement? Are we just strolling across town to score bottles of it from
>the local health food church, and then grinding it down in the kitchen?
>
>Jan Arnow actually advances the claim that sodium citrate can be
>substituted
>(93 parts of s.c. instead, due to their different weights). But I'm not
>sure
>I trust Arnow. This wouldn't be the first time her claims have made me
>suspicious, in the light of more contemporary writers on the alternative
>processes. On this particular point, I'd rather act on the advice of
>somebody who's perhaps more knowledgable in chemistry.
>
>Can anybody hold my hand on this, and point me to safe harbor?
>
>Mike Healy
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