Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Mon, 24 May 1999 23:57:24 -0400
Dan Koons wrote:
>
> I understand some printers use a solution of potassium chlorate for pt/pd
> in place of the #2 fo for the develop out printing. what I would like to
> know is if there is a chart for how much to use. for example what would one
> use in a formula that would replace 3 drops #1& 3 drops #2?
Dan,
I would strongly suggest that you change from using prepared solutions
such as #2, #3 or whatever and mix you own solutions from dry stock
chemicals. This will give you much better consistency and reliability.
I have several one ounce dropper bottles with various contrast
solutions. Potassium chlorate is mixed to 1/8, 1/4, 3/8, 1/2, 3/4, 1, 1
1/2, and 2 percent solutions. For a 4x5 I may use anywhere from 1/8 to
1/2. For an 8x10 I may use from 1/2 to 2. These jumps are enough to be
noticed and within the operation of most materials including papers.
I also use Potassium Dichromate and know Ammonium Dichromate as contrast
agents. I have used Hydrogen peroxide but have stopped except for a
rare occurrence. The H2O2 must be made fresh as it breaks down
rapidly. This makes consistent results questionable.
As to a chart for the use of a contrast agent, I would strongly
recommend against the use of such a chart. Each negative and at times
each print will request their own amounts. It sort of like cooking;
instead of precise measurement, the chef adds a dash of this and a dash
of that knowing they've got the right feel of it.
I do not submit to the statement made by Bob Schramm:
> Frankly, if you start with a good "platinum-engineered" negative
> there is no need for contrast control.
Indeed one starts with the best negative they can. But we all know it
ain't goin' to be perfect. By golly, if there weren't tweakin' and
fiddlin' just any ol' person could make the print. Believe me when I
say: THERE IS ALWAYS A NEED FOR CONTRAST CONTROL, and exposure control,
and printing discipline. So often it's the nuances that make it or
break it.
Remember too that CONTRAST may be influenced and controled by type and
mixture of chemistry, exposure, paper, ambient conditions, processing,
and I may have missed some others.
Now don't for a minute think that a great print can be made by random
tweaking or even educated individualized tweaking; Pt/Pd is a process in
which many facets must be mastered and controlled. Perhaps similar to a
symphony orchestra in that each instrument must be masterfully played on
its own as well as integrated and related with the rest.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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