Digital BW, The Print

Paul, you wrote:

> I've done the usual alignment that is accessible via the driver.  I've
also
> checked the B & C Head Slant/Height adjustments through the 7500's display
> panel.

Then you are already in service mode for adjusting the heads manually
(screwdriver included). So you have covered all adjustments. It is however
important to do it with the inkset + paper that will be used in printing
later on.

> > With the 9500 and Generations inks most users got
> >better results with the 9000 driver. The Generations inks
> >were mixed for the 9000 dye generation. The 9500 higher voltage
> >to the nozzles may be an advantage for
> >the UC clones as their rheology probably is different, could
> >be that the 9000 driver isn't then the best choice either.
>
> Is there more to "rheology" than viscosity?  (I'm not a chemist.)

It belongs in the physics department I guess. Viscosity, tixothropy, surface
tension, capillary action, electrostatic load etc. Not only on flow in the
ink channels but how it will act in the piezo pump chamber, droplet
formation, impact on the coating, adherence to the coating, flow in the
coating's absorbers. High speed camera shots of droplet formation at the
nozzle exit, that kind of stuff.

>
> One of my theories in purchasing a 7500 was that, being made for pigments,
> it might be better for the pigmented inks I use than the 7000.  For
example,
> it has been my impression that the new "high-load" pigmented inks are
close
> to the limit that standard desktop printers can handle.  Also, I think,
that
> the pigmented printers might have some firmware (?) routines for cleaning
> that may be useful.

There's an additional heavier cleaning in the 9500 firmware compared to the
9000. On the US Epson site there's a firmware upgrade for that purpose.

> When doing curves for the 7000 and 9000, what I noticed with them is that
> the Epson driver gave a lower dmax than the desktop printers.  The 7500,
on
> the other hand, is said to pump out a lot of ink.  That may also be the
> voltage difference you mentioned.  The dmax I'm getting with the
> "Watercolor" paper setting is higher than my 1160.  So, it looks like the
> 7500 does have a better dmax than the 7000 with the Epson driver.

For some time I'm thinking that there is one advantage in the older pro
printers. If you need the heaviest ink load it is unlikely that you get that
with the latest models that combine higher speed with finer droplets and
higher resolution. The density can be increased with higher pigment loads
per ml but there will be a brick wall where the ink viscosity needed for
higher pigment load suspension is too low for the maximum piezo pump
activity possible (at high speed and resolution). To keep the high pigment
load suspended while the ink is static and still get flow at the pumping
action is the trick. Increasing tixothropy is then the way to go, it also
gives a better setting of the ink at the coating so less bleed. Not so nice
for gloss printing though as the ink sets before it gets into the coating.
Glyzerine is most likely the stuff used in the highload pigment inkjet inks.

In offset and silkscreen printing the finer the screen resolution the
thinner the inklayer has to be otherwise dotgain gets out of hand. That
limits the maximum density as well. Making the ink more tixothrophic and
giving it a higher pigmentation will end in less gloss and problems with the
water balance in offset printing. Inkjet printing has more similarity with
(roto)gravure printing (the diazo dyes for example) but part of those rules
will still hold if it was just the detail contrast maximum. That was
gravure's achilles heel.

The 9600/7600/10600/2200 have the advantage of the grey ink of course. Where
3 inks were needed to get a grey with a certain density  there's only one
grey ink needed that probably has a slightly higher density than the darkest
of the CMY inks. Not only does it control the neutrality better it also
reduces the inkload and so less bleed (dotgain) at the same density.

>
> If I do try the 7000 driver, is that anything more to it than just
> downloading/installing it?

For the 9500 it is just like that. I guess it will be the same for the 7500.
Diana York uses the 9000 driver for her 9500 that was (is) loaded with
Generations.

Ernst