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Re: Cold Bath Developer - PT/PD

NIck, The cold bath developer is listed in a number of text.  I have it
within the pages of a Kodak Guide to Practical Photography printed by in
1978.  It has several different formulas but the essence is that about 180g
Potassium oxalate with 50 to 60 grams Potassium Phosphate mono basic.  The
powder potassium oxalate is sold by B&S, the Formulary, Artcraft, etc.. It is
very expensive compared to making it yourself with potassium carbonate and
oxalic acid which could be a very good reason Dick left it out of his book on
platinum printing. :)?

You should be able to dilute what you have made just short of 1:1 with water
and add the potassium phosphate mono basic.  The Formulary also sells the
potassium phosphate mono basic.  It may give you a bit more contrast than the
standard PotOx developer.   You can dilute your standard Pot Ox with water
and it will give you a print that is slower, and with more contrast but it
will have more grain or at least that is what I saw with those combination of
processing elements.

the potassium oxalate developer that you have made is close to saturation.
This could explain the need to dilute it in order to add something else to
the solution.

Hope this helps

EJ Neilsen



Nick Makris wrote:

> I have run across a formula for PT/PD Cold Bath Developer which is as
> follows:
>
>         175 gm Pot Oxalate, 75 gm Pot mono Phosphate and 1 qt. H2O
>
> The implication here is that Pot Oxalate can also be a dry powder (it was
> probably first a dry powder).  However, I only know Pot Oxalate as a
> solution prepared from Pot Carbonate and Oxalic Acid.
>
> The question is, how would one go about modifying the above formula to
> prepare a qt. of Cold Bath Developer if you were to start with a quart of
> Pot Oxalate in solution form, or could you???
>
> Seems like one would just add the Phosphate - but as we all know it's
> usually not that simple.
>
> Many thanks,
>
> Nick

--
Eric J. Neilsen
4101 Commerce Street, Suite #9
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