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