[alt-photo] From colour transparency to black & white separation negatives for contact printing?

[Tom Kershaw]

First post to the new list:

If one wished to produce separation negatives (e.g. for colour gum
dichromate printing) from an in-camera original transparency in the
darkroom are any suggestions forthcoming as to an effective procedure?
Firstly, are there any advantages to be gained by using an
orthochromatic film (e.g. ILFORD Ortho or Adox Ortho 25) aside from the
ability to work in safelight conditions?

Here in the United Kingdom, Fomapan 100 is to the best of my knowledge
the least expensive film available while still apparently maintaining
reasonable manufacturing quality control. Has anyone on this list used
the Foma film for the purposes of making separations? In terms of
technique, I would assume the use of enlarger filtration controls to
create red, green, blue tinted projections to be used for cyan, magenta,
and yellow (approximate) layers in the print. Although I don’t have the
reference to hand, I recall ‘DK-50’ has been suggested as a film
developer for separations perhaps due to its supposed high contrast
results. Any suggestions on starting points for relative exposure and
development between the negatives?

Tom Kershaw