Digital BW, The Print

> But arguably one could make a "dye" ink of very small carbon particles....

My understanding is that dyes are soluble and pigments are not.  Only if you
consider molecules to be particles do the two meet. 

I believe the carbon that is used in the black ink is mostly graphite.
Graphite is insoluble in water.  See
http://www.hummelcroton.com/data/grph_d.html


But, it is true that the particle size is probably the most important
distinction.  

It is also my understanding that the dye printers can use low loads of very
finely ground pigment.

Apparently one thing that limits the non-Epson desktop printers in this
regard is the viscosity of the inks.  The piezo-electric head that Epson has
rather well protected with patents may be the only one that can pump the
high-viscosity base needed to keep high loads of larger particles in
suspension.  So, for example, the dye inkset blacks may well have carbon
particles in them.  But, there will be a relatively low load (relative
amount of pigment per volume or weight), and the particles have to be very
finely ground.  (The smaller the particle, the lower the viscosity needed to
keep it in suspension.)  The good dmax they get comes from the dyes that are
added, and the composition of these is unknown to me.  They used to be color
pigments, particularly cyan.  (That is where the PKN concept came from.)


Paul
www.PaulRoark.com