The "delta B = 2" Northernlight test image on Arches is posted here:
The artifacts I was trying to trace down are visible in the top, small circular gradient. The non-linearity appears to be an artifact of linearization that just shows up worst in the black ink and small, high contrast gradients. I have been unable to trace the exact cause(s). They show up in a 2 inch print using a linearized Black Only profile gradient, but not in a 6 inch print, even when the 6 inch gradient is compressed to 2 inches after it is scanned. They do not show up in the un-linearized profile gradient. I have never seen evidence of this artifact in actual pictures.
At any rate, I think from the posted scan of an 8x10 image, one can get an idea of what a full sheet Arches 100% carbon print made this way would look like. On the wall, with a natural paper mat board, an image made with this "dB2" profile is going to look simply like a neutral B&W print.
This "glossy" carbon inkset is turning out to have abilities I did not expect.
Paul