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Re: platinum/palladium coating - exposing POP
Istvan , Are you mixing your AFO and lithium in a batch and then dispensing
small amounts for each coating? You also failed to mention your procedure.
As this list has kicked around, there are many Blank o types when it comes
to making what once might have been called a platinum print, so it is
important to trouble shooting to let us know what else you are doing.
The glass may warm up to higher than acceptable levels. Rather than several
contact frames, I use different pieces of glass. This not only lets the
glass cool back down after use, it allows me to set up another negative for
printing with any light blocking mask, borders, etc, that the print
requires.
I don't make many pure lithium palladium prints, but all that I recall are
quite cool much like a platinum only print.
I would also suggest that you can use a small fan to help remove the hot
air from under the light source. While your glass will still warm up some,
this will help tremendously.
Eric J. Neilsen
4101 Commerce Street, Suite #9
Dallas, TX 75226
214-827-8301
http://e.neilsen.home.att.net
http://www.ericneilsenphotography.com
----- Original Message -----
From: "Jeffrey D. Mathias" <jeffrey.d.mathias@worldnet.att.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, April 09, 2001 5:50 AM
Subject: Re: platinum/palladium coating - exposing POP
> Istvan Bibo wrote:
> > I use ammonium ferric oxalate and lithium palladium chloride. I have the
> > problem of having only one deep black contrasty print (that i really
like)in
> > one printing session, the others are browner and less contrasty. I was
> > trying to figure out, what made the difference,because the conditions
were
> > kept the same.
> > Now I am almost sure that it was the freshness of the solution that made
the
> > difference, because the unrepeatable black prints were the first ones in
the
> > sessions. ...
>
> Perhaps. However do not be too sure that the conditions were the same.
> Did you monitor the temperature of your contact printing frame?
>
> I have found that after a couple prints the printing frame warms enough
> to alter the color (toward warm) of the print usually in a non uniform
> manner. This is likely due to a change in the RH (relative humidity of
> the coating) from the higher temperature). The result would be as you
> describe cooler color shifting toward warmer (and lighter blacks).
>
> A solution is to let the contact printing frame cool between exposures.
> If one has a lot of prints to make, they should consider getting a
> second or third printing frame. They can be rotated so they have time
> to cool. The temperature can be measured with a flat thermometer
> (liquid crystal type) placed in the frame. I have noticed the glass to
> be warmed to the touch. Another solution might be to build a
> temperature controlled frame (water cooled or such).
>
> Using the sun might produce more of a challenge as it will heat the
> frame much more. (I have not used the sun for POP, but have done plenty
> DOP with that light source.) Using UV lamps will produce enough heat to
> cause this problem. This is dependent on the exposure times, number of
> previous exposures, and rest between exposures. I found differences on
> the third or fourth prints with exposures of 6 to 8 minutes. Keep in
> mind that an exposure longer than 20 minutes may not be able to maintain
> and control temperature or the proper RH.
>
> I have found that in order to maintain consistency and get the coolest
> color, the temperature should be kept below 70F and the RH at 70%.
> Lower RH will warm the color. At higher RH, results will become
> inconsistent. Higher temperature can be inconsistent and may produce
> some other problems (especially over 85F, definitely over 140F which can
> occur when using the sun). Lower temperature is OK.
>
> --
> Jeffrey D. Mathias
> http://home.att.net/~jeffrey.d.mathias/