<<<Practice will show that if there is brown gunge all over the
negative,
offering a higher base + fog reading, then the negative will be
flattened
by the amount of the increase. >>>
The pyro stain is not brown gunge, nor all over the negative. It is
yellow/green stain (good at stopping UV light) and it is *proportional
to the silver*. FB+F on HP5+ is not affected (it is a different color
but no denser, and prints to a convincing black at the same exposure
time as a conventional negative on this film) but as silver density
increaes, stain depth increases even more, raising effective contrast
dramatically. Internal contrast--close value separation--is also greatly
enhanced but I don't know yet whether this is due to the stain or to
something different about the silver image itself, or some
combination/interaction of the two.
Kerik has said that pyro also works very well with FP4+. That film, as
you've pointed out, is a "natural" for platinum negs even with standard
developers (as are Kodak TXT and TMY) so perhaps Kerik can comment on
what improvements he sees by switching to pyro with it. I haven't tested
FP4+/pyro yet, but will soon.
<<<If one is using long
exposures to obtain in camera negs for platinum printing, the films
mentioned in this thread such as Agfa 100, HP5 and TMax and Tri X are
not
designed for the purpose.>>>
I'm not sure what you mean by long exposures for in camera negs--my
exposures for 8x10's on sheet Tri-X range from about 1/8 at f/45 in
strong sunlight to several minutes deep in the woods. All can yield
beautiful tones in Pt/Pd prints simply by developing the negs about 60%
longer than would be normal for silver printing. TMax-400 also works
very well. My tests of FP4+ in standard developers showed that it easily
reaches (and passes) the contrast needed for Pt/Pd, but is painfully
slow, needing 1/2 second at f/45 in full sunlight to retain decent
shadow detail. Working in the New England woods would be torture because
of reciprocity failure at typical light levels: I'd need hour-long
exposures. HP5+ is tricky to coax into producing a platinum negative in
standard developers, but responds beautifully to PMK pyro.---Carl