Digital BW, The Print

Tom,

You wrote:

>I DON'T want to start a round of Piezo ink bashing...But ...

>If [Piezo & MIS FS] are so similar, why do you think there
>have been issues of
>Piezo clogging and then the MIS inks working on the same
>printer...

I'm not sure, but I have several theories.

I think one of the main differences is that the Piezo midtones -- where the
problems seem to be mostly -- use the co-solvent ink.  (This is the source
of the bad smell.)  This ink is both more volatile than the base that MIS
uses in the midtone inks and it, according to one article, causes more ink
crystal "aggregation" (clumping), in part because it is a less effective
solvent.

So, the more volatile nature may make it more subject to loose CIS fittings
and drying on the heads.

As the solvent evaporates around the CIS, it may pull the soluble greenish
dye out with it and deposit it around the CIS.  Perhaps it also concentrates
it in the ink near the outlet.

MIS midtones, lacking the dye and the volatile co-solvent may be much less
subject to these problems.

MIS VM and FS black inks do use the co-solvent.   My sense is that neither
the Piezo more MIS VM or FS blacks have serious problems.  Since the black
ink does not have the greenish dye, it may be that the dye is a big part of
the problem.

The co-solvent aggregation may be happening too soon -- like in the heads or
on the screens in the heads.  Some CISs had the screens in them that the MIS
CFSs have.  I consider these screens important to have.  However, the
co-solvent plus dye combo might have been clogging this screen, letting more
of the soluble greenish dye through than the pigment particles.  This could
have been the source of the "green" problem.

I'm, of course, simply speculating.  However, I think the co-solvent and dye
combination in the midtone inks is the source of the trouble.

Paul
http://www.PaulRoark.com