[pure-silver] Re: Adding Pot Bromife to PC-TEA
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: "'pure-silver@xxxxxxxxxxxxx'" <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 7 Jan 2005 17:35:10 -0500
Thanks for that suggestion. The potassium bromide is difficult to dissolve.
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. 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.
Jerry
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx]
On Behalf Of Ryuji Suzuki
Sent: Friday, January 07, 2005 5:07 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Adding Pot Bromife to PC-TEA
From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
Subject: [pure-silver] Re: Adding Pot Bromife to PC-TEA
Date: Fri, 7 Jan 2005 15:51:38 -0500
> A few weeks ago Gainer changed the formula in an APUG post by reducing
> the amount of Phenidone to 0.225 g.
I don't know what that small change offers. Activity of phenidone type developer
changes slower than a linear relation when the concentration is changed.
> This helped a bit with
> the contrast/density problem. Soon after that someone suggested
> adding 0.25 g of potassium bromide to the concentrate. This really
> cleaned up the negatives and greatly improved the contrast/density
> problem.
There are some published data that compared the effect of a bunch of
antifoggants in terms of suppression of developer fog and absence of suppression
on weakly exposed grains. Bromide isn't the best on this one, and you can easily
avoid the problems you're having by using 1-phenyl-5-mercaptotetrazole. You
should get a gram or two, which is enough to make a few hundred liters of
developers.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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