From: Joe Portale (jportale@gci-net.com)
Date: 03/31/02-03:03:39 PM Z
Clyde,
If I'm reading your email properly, you are using 20 watt tubes. You are
only getting about 160 watts. Most light box builders use 40 watt lamps. I
did the same thing with my first light box. The current box was built around
the 40 watt lamps and more tubes. Although not truely linear, if you swapped
to 40 watt units, your printing time should be cut in half. You could also
try this, do a couple test exposures in the sun. If the printing time stays
painfully long (I live in Tucson and sunlight prints take only about six to
ten minutes), look at your chemistry. Good luck.
Joe Portale
Tucson, AZ
> >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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