Clearing of Iron Salts in Pt/Pd paper

Stephen R Harrison (SRH@StephenHarrison.com)
Wed, 12 Nov 1997 22:31:55 -0800

I typically use 5 clearing baths of phosphoric acid 3% sol'n five
minutes per bath for 50/50 pt/Pd prints to clear Bienfang 360, and
platinotype paper( Not Platine !)
Every two prints, I discard one tray of clearing bath and replace with a
fresh bath. The prints do in fact appear clear and have no yellow stain. If
I however then place the print in a 6th bath of Kodak hypo clearing agent(
Stock Solution Strength) , I will usually find a slight yellow coloring in
the final bath after 5 or 6 prints go through the bath . I assume this is
the remaining iron salts that have managed to remain embedded in the fibers
of the paper . The Kodak hypo seems to me to be an extremely effective
clearing agent.
(1) What about the use several types of clearing agents such as two
baths of Phosphoric Acid 3% followed by one of EDTA followed by say Kodak
hypo clearing agent. Is there an advantage of using different types of
clearing agents for the same print to insure the iron salts are removed? Do
each of these agents utilize a different mechanism in clearing the print?
(2) As I understand it , the Kodak hypo clear opens up the fibers
of the paper. Should that agent not be used first so the citric acid or
phosphoric acid or whatever can get access to the paper more readily?
(3) What about combining different agents such as a combined 50/50
bath of phosphoric acid (3%) and Kodak hypo clear .
(4) Any comments re the relative effectiveness of citric acid vs
phosphoris acid ?
(5) I very definitely have trouble using only EDTA as a clearing
agent no matter how many baths I use? Anyone use only EDTA to clear pt/pd
prints? For which papers?