Eric Neilsen (e.neilsen@worldnet.att.net)
Mon, 24 May 1999 21:28:55 -0500
Jeffrey, there are two issues that your post brings up.
1) Does the pH of the ferric change the nature of the prints? and
2) Does excessive Oxalic acid help the ferric oxalate.
The pH does affect print quality differently with various papers and platinum to
palladium concentrations. In conversations that I have had with Martin Axon, he
claimed to see a difference in the way platinum reacted with platine. It was
beneficial to have a lower pH, more oxalic acid, with platinum. I have not run
extensive test with it. Since the question was geared to platinum use only, I
thought that Witho should consider giving it a go...
2) Historically, an excess of oxalic acid was believed to extend the life of
ferric. In the making of "ferric oxalate", I use 35% hydrogen peroxide and oxalic
acid. If you have "old" ferric that is fogging, you can try and fix it, by adding
small amounts of oxalic acid to convert the ferrous back to ferric. It may not go
into solution without heating though and then you run the risk of making more
ferrous. I think Dick posted some test that Rudiak and Kennedy were doing with
this. It should be noted though, that while excessive oxalate is ok for
platinum/palladium printing, it is not so with kallitype. Each method of making
ferric oxalate has its' own draw backs.
I may be able to run some test, but not until after end of July when I get back to
Dallas.
"Jeffrey D. Mathias" wrote:
> Eric Neilsen wrote:
> > ... You may also
> > consider adjusting the pH of your ferric, downward with a little Oxalic acid.
>
> Eric,
>
> I am curious if you have examined any relationship of PH and print
> quality outcome.
> Traditionally it has always been thought that the addition of Oxalic
> acid to the sensitizer was a beneficial thing, but I have never seen any
> proof of this even though I add the Oxalic acid because that was the way
> I was taught. I would certainly be interested if you have any print
> supported data on this or could you be encouraged to run some
> experiments.
>
> --
> Jeffrey D. Mathias
> http://home.att.net/~jeffrey.d.mathias/
-- Eric J. Neilsen 4101 Commerce Street, Suite #9 Dallas, TX 75226 214-827-8301 http://home.att.net/~e.neilsen
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