[pure-silver] Re: I say Ammonium you say Potassium

Thanks Richard!
Blumann's book here is circa 1937 and my edition of
Anchell's Cookbook is from 1994 so over a wide spread
of time nothing changed in my references...although I
wasn't around for Blumann haha!

Too bad for me no one made any published notice of the
ability to substitute Pot. for Amm. that I could
easily find.

Eric

--- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:

> 
> ----- Original Message ----- 
> From: "Eric Nelson" <emanmb@xxxxxxxxx>
> To: <pure-silver@xxxxxxxxxxxxx>
> Sent: Tuesday, August 21, 2007 11:16 AM
> Subject: [pure-silver] Re: I say Ammonium you say
> Potassium
> 
> 
> >
> 
>     More research: Kodak did indeed change the
> formula!  My 
> source for the formulas with Ammonium Persulfate are
> the 
> patent and the Kodak and Agfa/Ansco versions as
> published in 
> the _Photo-Lab-Index_, 1944 Navy edition. This
> version is 
> also printed in the 1943 edition of the _Kodak
> Reference 
> Handbook_. However, in the processing section of the
> _Kodak 
> Reference Handbook_, 1946 edition I find that the
> formulas 
> for both T-21 (Nelson's Gold) and reducer R-5
> specify 
> Potassium Persulfate. The same formula is found in
> the 1953 
> reprinting of the 1947 (third) edition of
> _Processing and 
> Formulas_ in the Handbook.
>     All of these include the instruction to refix
> the prints 
> after toning but this was left out of one of the
> editions of 
> the _Processing and Formulas_ booklet with a note
> added that 
> the results of Nelson's were not as permanent as
> other Sepia 
> toners. Of course it wouldn't be if it left halides
> in the 
> emulsion and they were not fixed and washed out.
> This error 
> occurs in AFAIK only one edition of the booklet.
>     The amounts given for the Potassium salt are
> identical 
> to those given for the Ammonium salt, which is, of
> course, 
> the anwser to the question: either may be used 
> interchangibly. This is also true for the Persulfate
> 
> reducer, Kodak R-5 where formulas showing both salts
> are 
> shown with the amounts identical.
> 
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
> 
> 
>
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