Re: What is green ?

Eric J. Neilsen ()
Tue, 14 January 1997 11:39 PM

On Wed, 15 Jan 1997, Jeffrey D. Mathias wrote:

> Eric J. Neilsen wrote:
> >
> > Jeff and Philippe,
> > When I make my ferric oxalate as per the Dick Stevens receipe in The
> > Difinitive Guide to Making Kallitypes it is a bright emerald green. I have
> > also made B&S ferric achieve this bright color by adding additional
> > oxalic acid and 30% hydrogren peroxide. Richard's Ferric has a tendency
> > to be a bit yellow/brown/green. It works great with a little help.
> >
>
> Eric,
>
> I add 1 gram oxalic acid to 50 ml ferric oxalate solution (27%) and
> somtimes use hydrogen peroxide as a contrast agent. However, I have not
> observed the solution to be a "bright emerald green". What is meant by
> "a little help"? I would appriciate if you would please send your
> formula.
>
> Also, what do you mean by 30% hydrogren peroxide. The type purchased
> from a drug store is typically 3%. 30% can be purchased from a chemical
> supplier, but caution must be used since it is a combustion and
> explosion hazard. Did you mean that to 20 ml ferric oxalate you add 10
> ml of 3% hydrogren peroxide ? If so this would seem to be far too much
> contrast for a properly processed negative for the Pt/Pd process. But
> maybe not.
>
> Jeff
>

Jeff,
Yes, I meant 30% Hydrogen Peroxide. It is used in the making of ferric
oxalate, as are oxalic acid and ferrous ammonium sulfate. In balancing
the final mix of a new batch of ferric, it sometimes requires adding a
little peroxide, than some oxalic acid, until the presence of ferrous ions
are not found. When I first began printing "Noble prints" ( my name to
add to the name discussion on platinum and palladium prints) we got our
supply of ferric oxalate from Tom Millea. It was always a bright green
color. It was after we started getting it from B&S that I noticed a
change in the color, more towards a brown green, or yellow green. No
slam on B&S, because their product works fine, but with the addition of
peroxide and oxalic acid, I find no stain/fog in prints that haven't
any additional boost added to the coating solution is needed.
wizard@laplaza.org (ie no chlorate, or additional peroxide)

How much to B&S ferric do I add? no more than .5ml of 30% to 100ml of
ferric, and between 2 and 3 grams of Oxalic acid.

Yes, 10ml of 3% to 20ml of ferric is NOT correct. That much would dilute
the concentration of the ferric and would be an indication of real
problems.

Eric Neilsen

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