Reflectance curves and color mixing

Hey all,
So I've been thinking lately about how different combinations of
pigments work for tricolor gum printing, and toward that end I've been
studying reflectance curves and thinking about the fact that in order to
mix saturated or even interesting intermediate colors, the primary
colors that are mixed must have corresponding peaks in the reflectance
curve; for example for a red to mix with a blue to make purple, the red
must have a peak in the blue/purple range. This is why cadmium red makes
really ugly purples when mixed with blues, for example, because cadmium
red reflects nothing but red and orange; the reflectance curve is flat
throughout the rest of the spectrum.

I've been sort of assuming that this rule holds also for colors that are
glazed over other colors, for example in tricolor gum printing, but I
don't know this for sure. I could spend some time testing the question,
but just wondered if anyone here knows the answer straight off. Thanks,
Katharine Thayer
Received on Mon May 30 14:24:51 2005