This method works with Potassium Oxalate developer only. As incrasing
amounts of Sodium Dichromate are added to the developer it increases in
contrast (and, as with other restrainers in other developers, decreases in
speed). Dick Arentz has the details in his book on Pt/Pd printing, but my
copy of his book is on loan to someone. Perhaps someone else on the list
can give the mixing and dilution formulae.
I like the method. I can coat many sheets of paper for a printing session
with the same sensitizer (w/no contrast agent), stick them in a light safe,
and expose and develop one sheet and if its off on contrast, immediately
expose and process another in a different contrast grade developer. I like
the exposing and prcoessing running at a rhythm uninterrupted by coating
and drying sheets throughout the printing session. The dichromate is very
stable, unlike Hydrogen Peroxide which used for the same purpose for
different developers. Some find it inconvenient because you have a bunch of
bottles of developer around, but I don't mind it. You can easily and
cheaply make a tempering bath that holds 8-12 1-liter bottles of developer
with a big kitty litter tray and an aquarium heater. If you tray develop it
means developer is being poured into and out of the tray with each change
which, admittedly, is a bit of a pain. The ultimate ease, which you've
heard me mention on many earlier posts, is to process the prints in a drum
with a rotary agitator. You could store your chemicals and process prints
up to 20x24 in the space of a 6' sink. Try that with trays!
Good luck and if I haven't seen details on mixing the dichromate on the
list in a few days I'll get my book back and post them.
Bill
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WILLIAM LAVEN PHOTOGRAPHY
Offering Platinum/Palladium printing services and workshops and tutorials
in Pt/Pd printing and other areas of photography (Zone System, etc.)
1931 23rd Street, San Francisco, CA, 94107
415-647-9432 (voice) 415-647-9438 (fax)
wmlaven@platinotype.com
www.platinotype.com
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