beginner seeks help---long pt/pd exposure times

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From: xrogers (xrogers@attbi.com)
Date: 03/31/02-01:52:00 PM Z


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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