Digital BW, The Print

Paul-

I'd almost forgotten the smell issue (how quickly we forget...this 
was overwhelming me in my fairly small converted wet darkroom). 

Your theory is the first one I've heard that squares with common 
sense... A solvent difference is about the only component that 
explains dramatically different results with the same model printer 
by different users. 

I keep having this nagging feeling that I really didn't try every 
single thing I could have to make the piezo inks work (at least for 
long enough to be able to test them side by side with FS), but the 
risk of wasting an enormous amount of time on it just keeps me in 
the "wondering" state, not the "jump in" mode <g>.

I posted in another message, a question about the idea of trying your 
VM mixtures with the piezo driver... Think I'll pop one in just to 
see what it does...

Thanks,

Tom O'Connell

TomOC@...
www.thomasoconnell.com



--- In DigitalBlackandWhiteThePrint@y..., "Paul Roark" 
<paul.roark@v...> wrote:
> 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