[alt-photo] Re: dilution of pt/pd

[Terry King]

Dear Eric


You don't need the over-complication of molar based solutions, it can be done just as effectively with a percentage solution if not more so. All you need to do is ensure that you are applying enough solution at the right dilution.


People have been getting good rich platinum blacks that way for 140 years !



Terry






It seems to me that the main point of making concentrated and molar-balanced
solutions of palladium(or platinum) and ferric oxalate is to ensure that
there will be sufficient concentrations of the solution per square inch of
print to yield a really deep black in those areas where the exposure is
complete. 







-----Original Message-----
From: Eric Neilsen Photo <ejnphoto at sbcglobal.net>
To: 'The alternative photographic processes mailing list' <alt-photo-process-list at lists.altphotolist.org>
Sent: Thu, 22 Jul 2010 3:40
Subject: [alt-photo] Re: dilution of pt/pd


I'd also camp under that flag. Diluting the coating solution can be OK, but
it doesn't take too long before the production of a viable black is
impossible. Balance is the key; extra solution may NOT be extra all, just
what is required.   

-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Clay Harmon Website
Sent: Wednesday, July 21, 2010 5:04 PM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: dilution of pt/pd

I have accidentally printed on a piece of paper coated with a 50% diluted
coat of palladium and ferric. The result was an anemic black and a generally
weak print. It also was badly solarized on the edges where the brush strokes
tailed out. This squares with my observation that solarization is most
likely to occur where there is too much exposure of too little coating in
the paper.

It seems to me that the main point of making concentrated and molar-balanced
solutions of palladium(or platinum) and ferric oxalate is to ensure that
there will be sufficient concentrations of the solution per square inch of
print to yield a really deep black in those areas where the exposure is
complete. Unless you print on completely wet paper, the water portion of the
solution has evaporated and all that is left is the solution, the paper
fibers, and whatever residual humidity from the coating solution remains in
the paper fibers. 


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