Digital BW, The Print

Paul Roark wrote:

> I'm curious about the filtering.  The IB-FS mix is going to need better
> high-shear mixing and filtering before it'll be acceptable for large format
> printing.  (The desk-top printer carts are easy.  It's the large,
> un-agitated carts where the problems are showing up.)  I'm hoping to try to
> design ways of doing this that will open the total pigment market to
> darkroom hackers like me (and artists who want to design their own color
> palettes).  The commercially-available products I've found so far are not in
> that category, in my view.  So, affordable 1 or 0.5 micron filters that
> don't soak up lots of (costly in low volume batches) ink are on the list of
> things to find.  The damper filters and MIS's large format CFS filters could
> be possible solutions to this issue.  As a practical matter, I might just
> recommend that every large format printer use a CFS for filtering and
> agitation reasons.

Strange enough you will find more about filters at the Schleicher 
und Schuell site, the company that owns Hahnemuhle.
http://www.schleicher-schuell.com
(they are now even in microarray technics I see)
The differences between the filters are size, particle size and 
their (non)hygroscopic behaviour. I only ordered some samples and 
they didn't work alright with inkjet inks. Can't tell you what 
you actually should use but there's an American S&S subsidiary 
that could. The Epson dampers were not that expensive and the 
inks were already filtered but contaminated later on (fungi, 
bacteria) so flow was not that difficult. That's stainless steel 
mesh, very tightly woven.

You probably need several filters after another with the 
possibility of backflush to get any results. We used a vacuumpump 
with an extra empty (wine) bottle in between to pull the liquid 
through. If you keep the feeding jar low and switch the pump off 
from time to time then there's some backflush. As a last step it 
may be better to use one of the Epson damper sieves as that's the 
final size you will encounter in practice.  Air has to be taken 
out as well, the vacuum can do this, additional nitrogen bubbles 
can take out the rest, don't know how serious this is but it has 
been mentioned before in inkjet ink manufacturing.  John 
Nollendorfs might help you with better information, he made the 
Wide Spectrum inks based on Ilford's Archiva dye. And he 
mentioned glycerol then.

CFS systems like the one I have made for the 9000 and the 5000 
(direct to the internal inklines) do not solve the pigment 
settling.  It can be better controlled if the tube in the bottles 
is 2 cm above the bottom but that's still no guarantee that it 
will work without problems. If gallons a year are used on one 
printer then it becomes different.  The big carts and especially 
the 9600 carts are better in practice with lower throughput, you 
can shake them regularly and the 9600 have seals that will not 
wear as fast from taking them out.  Micro organisms get into the 
CFS systems easier than in carts.  I wouldn't recommend an extra 
filter other than the original damper in any ink supply system. 
It could be different for the desktop printers where the 
filtering function in the cart is based on the content of one 
cart only and the larger sieves of the wide formats could act as 
a first filter in the CFS.  For that reason I once send a 9000 
damper to Eddie Matejowsky (Eddie's Chip Hack) for his 2200 CIS 
system. But the actual filtering should be done before printing 
time and not at printing time.

Ernst