Digital BW, The Print

>... Still not sure how the driver knows to turn on the black ...

The driver looks at the RGB values and starts to substitute black as the 3
curves approach the black point.  Take a look at some of the UT-3D curves
for glossy paper and you'll see where I have to turn the blue curve upward
to stop the Eboni from being injected.  In UT2 curves, when the red and
green curves are very close to black, the blue curve (sepia ink) becomes, in
effect, the black ink curve.

Paul
www.PaulRoark.com