From: Carl Weese (cweese@earthlink.net)
Date: 03/31/02-02:45:49 PM Z
Clyde,
Is your ferric oxalate standard or the "number two" containing contrasting
agent? Using that could result in long exposure times. I keep hearing bad
reports about "platinotype white" (presumably Cranes Cover Flourescent
white)--the only time I tried it the results were inconsistent, sometimes
giving slow, high-contrast, gritty prints. The old developer could be a
problem, and I find potassium oxalate generally much better than ammonium
citrate anyway. With a standard FL-tube lightsource, I get three or four
steps of max black from a Stauffer strip in ten minutes or less. Maybe
someone else will have input on those specific tubes.---Carl
--
web site with picture galleries
and workshop information at:
http://home.earthlink.net/~cweese/
----------
>From: xrogers <xrogers@attbi.com>
>To: alt-photo-process-l@usask.ca
>Subject: beginner seeks help---long pt/pd exposure times
>Date: Sun, Mar 31, 2002, 2:52 PM
>
> Hello, all. This is my first message to the list---a couple years of
> lurking bites the dust.
>
> I'm trying out platinum/palladium printing. My exposure times to get two
> steps of maximum black on a Stouffer step wedge are more than 30 minutes,
> and I'm doing about 20 minute exposures for negatives.
>
> I'm using a home-built light box with 8 Sylvania F20T12BL tubes (about 1/4"
> between tubes) and two UltraLux electronic ballasts. My printing frame puts
> the paper about two inches from the tubes. I took the basic design from the
> Edward's Engineering web site (which claims the box should expose pt/pd in
> about 5 minutes), and got pointers to the ballasts from Sandy King's
> excellent UV light source article.
>
> My palladium salts are about six years old, and platinum and oxalate are a
> month old, from B&S. I'm coating crane's platinotype white with a glass
> rod, and using about 16 drops total for the 4x5 step wedge. Developer is
> ammonium citrate, about six years old, at about 85 degrees. Oxalate and
> salts are room temperature, between 60 and 65 in the Minnesota basement. I
> do get a decent black with enough exposure, so I've assumed I don't need to
> warm up the salts.
>
> So, are these times to be expected? Have I messed up the light source
> somehow? Is there an easy way to test the light's intensity? Am I doing
> some other obvious, stupid thing along the way?
>
> Thanks for any help,
>
> --clyde rogers
>
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