>My thanks to Terry King, who earlier this year spearheaded an English
>position to deal with contrast control via platinum-palladium
>concentration variation vs the more American position of dealing with
>contrast control by using chlorates.
Somehow I've missed the details on this procedure, so if anyone can fill me
in I'd appreciate it. It's nice to hear that the pt/pd ratio is going up,
it's good for business.<g>
HOWEVER! I've been working on this problem from the other end. The new
Ziatype system which makes pure palladium prints has an enormous contrast
range without graining. It will produce a pure black, browns or grays or
purples and blues. No platinum needed. (OK, I was out to lunch when they
gave out business brains!) Charles Palmer of the List has been working on
the sensitometry and concurs that there are some dynamite dmaxes to be had.
I've added up to 4 drops of 20% ammonium dichromate to the mix for
increasing contrast. That's right 20%! The print times in my F20BL
fluorescent light bank (Edwards Engineering brand) run normally 1.5 to 2
minutes; with the 20% amm. dichromate, the times went to 18 minutes or 3 stops.
The Ziatype system used Lithium chloropalladite and/or cesium
chloropalladite and ferric ammonium oxalate as the basic ingredients.
A more complete document on the Ziatype can be found on George Smythes
homepage at //www2.ari.net/glsmyth/.
John Barnier of the list just informed me that he has found that lithium
chloropalladite and potassium chloroplatinite makes a good POP toner. He
says that the sodium chloropalladite bleaches the image.
Dick Sullivan
Bostick & Sullivan
505-474-0890
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