Since neutral tone prints seem to be desired by inkjet printers It is somewhat surprising to me that none of the ink suppliers for inkjet printing market the more neutral Lampblack (PBk 6). In carbon transfer printing we use this pigment for neutral tone (or slightly bluish black) prints. Lamp black is a variant of Carbon Black (PBk 7) that is very stable and unaffected by light, acids and alkalis. Some types of PBk 6 may have a brownish black tone similar to PBk7, but the bluish black is more common.
Sandy
There is no carbon ink I know of that is the same as or as neutral as the old, original Eboni MK and it's dilutions. Eboni 1.1 is said to be the same carbon grind, but with a state of the art dispersant. That may be true, but the new dispersant made it more like the other MK inks. It's still slightly more neutral that the others I tested, but there is a reason I added the light blue toner. I concluded it was still the best place to start.
Inkjet
carbon (i.e., carbon that is finely ground) is warm by nature, except
when it's at the 100% black point. On inkjet paper (coated paper) it's
warmer than when on a paper like Arches. Glossy carbon is warmer than
matte carbon. And when glossy carbon is on glossy inkjet paper, it's
very warm. I, too, have found no way to make a neutral glossy 100%
carbon print. The good news is that with the Canon based light blue
toner, the print can be more stable than a silver print.