From: Sandy King (sanking@clemson.edu)
Date: 12/31/01-09:05:44 AM Z
Carl,
There was an increase in effective film speed with the phenidone
version of Pyrocat when I compared it to metol in laboratory tests.
Although the increase is small - less than 1/4 stop - and might not
be observable in field photography, I decided that the gain in speed
was worth the trade-off in loss of stability of Solution A of the
stock formula.
For those who prefer to use metol, substitute it at about 10X the
amount of phenidone specified in the formula. Also, it is probably
best to add it to the solution before the bisulfite.
Sandy
>Sandy,
>
>What is the reason for the switch to phenidone, especially if it results in
>limited shelf life?---Carl
>--
> web site with picture galleries
> and workshop information at:
>
> http://home.earthlink.net/~cweese/
>
>----------
>>From: Sandy King <sanking@clemson.edu>
>> I mention this because the shelf life of Pyrocat, when
>> mixed with phenidone, is probably no greater than about three months.
>> When the Pyrocat stock solution goes bad the result is a lot of extra
>> base stain, somewhat irregular - even splotchy- and very observable
>> on the clear edges of the film.
--
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