[pure-silver] Re: Adding Pot Bromife to PC-TEA
- From: "John Black" <jblack@xxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 7 Jan 2005 18:11:52 -0500
>
> I have always thought that Gainer's formulas tend to use too much
Phenidone.
> His initial P/A ratio was 1:36 (0.25:9). If you make the necessary
conversions
> in the Xtol formula you get a ratio of 1:69. Some other commercial film
> developers are even smaller 1:80 or 1:90. I was wondering if this was the
cause
> of the fog and poor tonal separation that I was seeing.
Too high pH is generally the cause of fog with phenidone.
Substituting 0.3 g of
> Dimezone-S instead of 0.25 g of Phenidone keeps the same ratio. However,
the
> substituted phenidones are said to be less efficient compared to phenidone
even
> when the difference in molecular weight is taken into consideration.
This is consistant with my findings. Phenidone is the most active of the
group, if you can stabilize it.
JB
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