Message text written by Carl Weese
>
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*.
I was over simpifying to make the point, but it remains that if the gunge
were not there one would get better results with Pt/Pd printing. So why
bother with pyro for a pupose for which it is not suited when there are
superior alternatives ?
<<<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
But if you want really good results you put up with the long exposures. I
have a formula for reciprocity failure for FP4 . Rate at two stops over
and add five further stops + prayer for anything over two minutes indicated
exposure. Works a treat. You can go off and a expose a few rolls of 35mm
during the ten eight exposure. This can have disadvantages. I once returned
to find a party of German tourists peering through the lens !
Terry