From: Sandy King (sanking@CLEMSON.EDU)
Date: 11/26/01-12:30:56 PM Z
Garimo wrote:
>
>So, my questions are, what are the differences between PMK, and
>>both ABC+ and Pyrocat-HD?
>Are some Pyro developers easier to use than others??
>
There are several differences.
1. ABC+ (1:2:50) and Pyrocat-HD (2:2:100 dilution) are much more
energetic developers, requiring only about 50% of the development
time of PMK to reach the same CI.
2. Both ABC+ and Pyrocat-HD are capable of a greater CI than PMK,
very important with the alternative processes when a DR of 1.5 is
needed for a normal scene of SBR 7.
3. In use PMK exhausts more than ABC+ and Pyrocat-HD. This results in
a pronounced shoulder and compensation in the highlights. ABC+ and
Pyrocat-HD show very little shoulder with normal development times.
4. The color of the stain is different. PMK and ABC+ with most films
give a greenish stain, or a yellow-green stain. The Pyrocat-HD stain
is more brown in appearance, with only a slight hint of green.
5. The PMK stock solutions are rock stable and will last for several
years. The stability of ABC+ appears to be about three months, and
Pyrocat, about six months.
As for ease of use, they are all about the same to me. Pyrocatechin
is less toxic than Pyrogallol so I don't worry as much when some of
it gets on my skin, but both should be mixed and used with caution.
Pyrocat can be used at either a 1:1:100 dilution, where it gives
results very similar to PMK, or at 2:2:100, where it is virtually
identical to ABC+.
My tests of these developers, all in rotary processing, show that
Pyrocat gives a slightly lower b+f than PMK and results in slightly
higher effective film speed than either PMK or ABC+.
Sandy King
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