when I explored 3-color-carbon some years ago, I thought it might be worth
considering to make the separations from color negs instead of transparencies,
as they contain more information esp. in the highlights.
To get the separation positives, I used the AGFA Contone P230p film, developed
in AGFA G5c developer, and the AGFA filters L599 (red), U525 (green) and U438
(Blue) in my old Homrich condensor enlarger. Developing time was almost the same
for all three separations. The film is also available as P330p and P440p with
increasing contrast.
For the second step (contact printing to get negatives) I used the AGFA Gevarex
GO210p. This orthochromatic continous tone type of film has a variable gradation
much like the modern vc-papers: yellow light makes it more contrasty, blue light
softer. Exposure and developing time can be kept the same after the first test
strips, you simply change the relation of yellow to blue light exposure. The
film has a rather straight curve between 0.25 and 2.75-3.0 logD and can even
reach a Dmax of 3.5-4.0 The film is available in two thicknesses on polyester
base, the GO210p being the thinner version and as GO230p with a thicker base for
ordinary film holders.
Note that these Materials are supplied by the AGFA graphic arts division. They
should be available in any size from 13x18 cm to 50x60 cm (50 sheets) and rolls
40, 61, 76.2 and 110 cm width, 30.5 m length. As they are made for machine
development, drying can even be accelerated to less then 5 minutes by squegeeing
the film with a (soft) rubber squegee before air drying. If you should have
difficulties to find an AGFA dealer, I could help you to get the materials from
Germany.
Best wishes for 1996,
Klaus Pollmeier