Digital BW, The Print

>>>>
No mistake.  The FS-K appears to do better in the 100% patch than in
midtones.  Although I must confess I was a bit surprised myself that
no warming at all occurred.  I've come to the conclusion that the FS-K
does have a bit of dye in it. ...
>>>>

When I first switched to inkjet printing with a PiezoBW system, the black
ink was described by Jon Cone as carbon that was "coated" with a colorant.
The PiezoBW black ink and FS black are essentially the same ink.  Cone now
says that the "coating" is a myth.  (I assume he was just passing on what
his supplier told him.)  However, when one considers the "aggregating"
effects of the co-solvent, the original description of the pigments as
carbon "coated" with a colorant (dye) may not be that far off.

Note that the very lightfast UC Matte K is composed of "proprietary dyes and
pigments" -- no carbon at all.  My reading indicates that many pigments are
"stacks" of azo dye molecules that do not dissolve in water and are, thus,
pigment particles.  So, the chemical line between dyes and pigments is not
so clear.  The pigment advantages come from their form as a particle with a
much higher mass per oxidizing surface area than the fine, thin coating that
is formed on the surface when dissolved dyes crystallize on the paper.

So, even assuming the FS-K does have some dye in it, as long as the
"aggregating" effect of the co-solvent does its job, it may act like it has
a lot less dye than it really does.  I'd say that the midtone FS ink
fade/warm performance probably shows the relative amount of dye that is in
the FS-K (FS midtones being FS-K diluted with non-co-solvent clear base),
and the FS-K black patch's relatively better performance may show how
effective the co-solvent aggregating effect is.

I think when one considers cost, depth of black and performance, the FS-K
will remain a good, competitive ink that may be chosen by many even if they
move to a tougher, more expensive, pure-pigment midtone.  Just like many
prefer the Media Street Enhanced black, which has much more dye and no
co-solvent, due to the deeper black.

Paul
http://www.PaulRoark.com