Digital BW, The Print

John,

You wrote, in part:

>I've been using the K6 in a 7000 for about 6 months and 
>there is no clogging and absolutely no ink separation problems...
>... It is the best in my opinion as long as you don't need glossy media.


All blended B&W inks I've had experience with (which excludes the K7 inkset)
show differing degrees of hue changes when left idle for more than a week in
large format printers.  The problem may not be settling, as such, but I
don't know for sure what causes it.

One thing I do in an effort to test the relative characteristics of
different pigments is to put a drop of the color or carbon pigment in a test
tube of the clear base I'm interested in.  Does the pigment stay in
suspension or not?  What I've found is that the magenta pigments from both
MIS and Epson settle somewhat.  The R 800 Blue from MIS does not settle.
So, that is the one I use in the MIS blended inks. 

Still, there is some hue shift in large format printers when they are left
idle too long.  The degree seems to be less with the R 800 Blue than with
the magenta, but there is still a hue shift in these blended inks.  

I have not seen this in desktop printers that do not have the tubing between
the heads and the carts.  The hue shift is also not seen in a printer that
is used regularly.  It's only the infrequently-used large format printers
that seem to be affected.  However, for individual photographers like me it
is an issue -- frankly, a nuisance.

My initial impression from just looking at my 7500 tubing, as well as the
beakers and other the things I use when mixing, was that the color inks
stick to things to different degrees.  Remember the early Piezo problem with
the sponge that seemed to cause a color shift.  In large format printers
(and CISs?) the tubing and/or the dampers may be having such an effect.
They may act almost like a catalyst in separating the colors. 

As far as I can tell, there is no settling of the inks based on the R 800
Blue in the carts of my 7500, for example.  I'm not guaranteeing it is not
happening, but once I've purged the lines &/or damper, the tones appear to
be rather stable from beginning to end of the cartridge. It acts like the
separation or whatever, is limited to the tubing &/or dampers.


At any rate, my observations relating to these separation issues are among
the factors that lead to my opinion that large format printers may be best
left to those who can use them regularly.  This, in turn, is one of many
factors behind my attempts to connect the individuals like me to the service
bureaus who'll be able to print my large ones.  I can probably keep a 4800
running well, but I'd love to get my too-large and seldom-used 7500 out of
my office (space being another major factor).  

With an inkset like the UT-3D, I and others can have ICCs that matched the
tones of whatever the service bureaus have.  "Color management" in the sense
of standard monitor views and print densities -- like Gray Gamma 2.2 or Dot
Gain 20% as shown on a calibrated monitor -- would be another essential
element.  With rips that don't use the standard ICCs, their outputs can
probably be adjusted to match the standard monitor views and output
densities of a "color managed" 220 output.  For example, I've been able to
match the standard Dot Gain 20% output density with IJC linearization
controls.  I suspect other rips can also be adjusted to match these
standardized output densities.

There is or should be no reason a large format K6/7 print can't be proofed
on a cheap 220 3D combination such that an e-mailed file can be printed and
tube-mailed back very efficiently.  


Paul
www.PaulRoark.com