Nick asked >>Something I don't understand is why I need to dry the drum so well
to avoid spots but I can do a pre-rinse and no spots.<<
Nick, probably because the paper is so very sensitive to water spots swelling
the emulsion and not giving you even development. when you prewet and soak the
entore emulsiion at the same time, nothing stands out. But when you get a few
water spots or runs from excesse water in the drum and the developer hits the
paper, you get a different pattern of development where the paper was already
wet.
As far as the difference between the raw stock color, there is a large change
in color from Supra III to Supra Endura. it has nothing to do with roll verus
precut sheets. The color you see and that comes out in the developer or
pre-rinse water is just sensitizing and other dyes used to make the paper.
These control the speed of the emulsions for batch to batch consistency, and
make each emulsion layers silver halide sensitive to the proper color of light
when it is exposed.
This dye does wash out during the process, and it should not make any
diffrerence whether you pre-rinse or not.
Bernie