A while back, I wrote that I couldn't get a long expanse of shiny white
stretch limo to develop low-contrast without mottling on either 12x18 lith
or N31P, using either brush development or dangling by 4 corners. David
Kachel's technique of open tube rolled in a tray was suggested -- a big
improvement, as I reported at the time -- not great with lith, but pretty
good with N31P.
Since then I have continued using tube for all large sheet film -- a much
easier way to handle those big floppy (3mm) sheets. Now I notice some
peculiarities:
For one thing, there's a dramatic difference between the test strip and
the final, full-size sheet. I haven't customarily done full-size tests, as
cost and waste for 3 to 4 tests mount. In past, adding 10 to 15% to
exposure and development seemed to compensate for the different way
developer hits test strip and the large sheet.
But I haven't gotten the hang of this for the tube, with, again, the
problem more noticeable with lith than N31P. Taping test strip into the
full-length tube near one end and carefully moving the tube across the
tray and back is still unpleasantly off the mark. Any observations or
advice on this (other than "use a whole sheet," which I already figured
out) would be welcome.
And a stranger phenomenon: The lith film (which, granted, is goosey) will
show development stripes, or more descriptively "rays," in the fully
exposed margin along the length of the film (top and bottom of horizontal
format). Not the short sides at the open ends of the tube, but the long
sides stretching the interior length of the tube. It seems that developer
cascades over the long edge, where sides of film don't quite meet in the
circle, in ways to cause uneven development. The effects are rarely
visible in image area, but still worrisome.
My assistant, who in a former life was a sanitary engineer, says they
spent a semester in school studying surface action of liquids (layer with
a name we both forget, an "l" word I think), and supects that's in play
here. It isn't visible in the less-contrasty N31P. (Both films, BTW, are
nominally the same 3mm, tho N31P seems to have thicker emulsion: it feels
slightly heavier in hand, takes much longer to clear.)
I'll add for those contemplating this generally superior method for
developing large film for low-contrast continuous tone, be sure to
position the sheet straight in the tube -- I suggest taping it at the
edges. When a sheet got loose and twisted over on itself, a less-developed
diagonal line appeared at the meeting place.
A final question: I've bought some 16x20 inch N31P (Arkin, 212-686-8805,
about $240 for box of 50), now need tube for 16x20, contemplate 16x20
print drum for closed-tube development -- to avoid large open trays of
chemical in small darkroom -- but have never used drum larger than Jobo
4x5. Would the time it takes to pour developer out and stopbath in be a
problem with very short development times (about 2 min for goosey lith, 3
min for N31P)? Of course it would! Any other comments?
And a footnote for folks contemplating tube development -- speed of
rotation is a BIG variable. I put a piece of tape on outside of tube to
mark the complete rotation point and time rotations (by metronome) --
about 8 seconds per roll for N31P, 12 for lith. A while back someone
mentioned "Speed 4" on a Jobo drum, but didn't answer when I asked how
fast that was. I'll add, however, that when I developed Kodak PCF in Jobo
tank, no mechanical speed available was slow enough. With HC110, it
required a 40-second rotation, with Rodinal, a mere 20 seconds.
End of report. Comments or advice about large film in tube welcome.
Judy