Digital BW, The Print

tboleyyh wrote:

> Charles, I'm afraid I'm not spending much time on the list any more, 
> but since your problems are using a workflow I've been
> involved with I've watched your posts.
> One comment. If truly, nothing at all has changed but the ink batch, 
> and going from carts to CIS, I'd say the new problem has
> to do with one of those two elements.

I've been following this as well.. and until you reiterated that point, 
I had simply passed it of to an ink batch variation...

But, then Paul's comment on viscosity differences in the Canon's and 
EPSON's must have jogged something loose..

It could well be the CIS, but in a sense that we may have overlooked..

The viscosity and density of the inks we use is generally tailored for 
short-travel from chamber to printhead..  Adhesion as a factor in ink 
travel over such distances is relatively minimal...  BUT, remember that 
the pigment inks ARE suspensions not really solutions... Suspensions can 
do very different things in the course of a length of hose/tubing/pipe 
than they may over very short distances.. Under certain conditions of 
ratios of suspended matter to to carrier fluid, suspensions can exhibit 
non-Newtonian properties... (Ketchup -- you hit it and it liquefies and 
Silly Putty -- you hit it and it solidifies even to fracturing; are the 
common examples)  It is possible that one of two things may be happening...

1)    Within the confines of the CIS tubing,  one of the inks is 
exhibiting more pronounced non-Newtonian behavior than the other mixes.

2)    Simple adhesion to the CIS tubing, during transit, of either 
carrier or suspended particulate...

Both should be relatively simple to test for..

To test for #1:

a)    I would look for changes in density of specific test  patches over 
the course of a print that had been done AFTER letting the CIS and 
printer sit for some time..  You would likely see that problem test 
patch become more or less pronounced as printing moved forward.. (as the 
non-Newtonian effect would predominate as ink traveled more 
consistently)  or you might see a brief problem in that patch where 
those forces predominate momentarily.

b)    The final density of a mostly consumed bottle of ink will likely 
in such a case, be  found to vary significantly, and non-linearly, where 
compared to original pigment density (as a ratio), in other inks w/in 
the same set..  In other words, one ink will be more out of whack than 
the others when you get to the bottom of the bottle.

To test for #2:

a)    You may also find item  (b) above happening..

b)    You may well find that one of the lines when fast drained, not 
purged or flushed, will show a significant residue of adhered pigment 
that is out of line with the other inks..


If  #1 is found to be the case, a new carrier fluid may be the best solution

If #2 is the case, simply establishing differing pigment concentrations 
or curves for CIS transported inks (when compared to cartridge carried 
inks) may be the easy solution..

Just trying to think "outside the box" here..

[Keith]
 




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