Digital BW, The Print

Jim:  

I'm not sure about the optimal percentage of air in the carts, but 
as Barry says some air is necessary to stop back syphoning or excess 
ink bleeding through the head onto the paper.  The vacuum fill 
method is not 100% efficient (can't achieve a perfect vacuum), 
therefore it always will leave some air in the carts. The amount of 
air left by the vacuum fill method has worked for me through 4 
installations.  

The real problems begin when there is an air leak into the cart 
either at the fittings on top or the ports on the bottom. The drawn 
in air replaces the ink that would have been drawn in and ultimately 
you get an ink starvation problem and/or an ink clot caused by the 
solvents in the ink diffusing into the enlarged air pocket.  
Diffusion of solvents (water, glycols, alcohols, etal.) through the 
plastic ink delivery tubes leaving a clot is also a problem, 
especially in a dry and hot atmosphere.

Jeff Randall

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Barry Kelsall" 
<bktimes@h...> wrote:
> Optimally the carts should contain 10-20% air in any CIS/CFS, so 
the air in
> the lines is no problem. More commonly, the problem is not enough 
air in the
> carts, which can cause bleeding on the paper, or siphoning of ink 
away from
> the heads, & more...  I am now a convert to the bottom-fill 
method, in which
> you can measure the amount of ink that goes in the cart 
precisely. -BK
> 
> 
> ----- Original Message ----- 
> From: "Jim Batzer" <jbatzer2@a...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Sent: Saturday, October 18, 2003 6:36 AM
> Subject: [Digital BW] Re: New CFS 1160 UT question (pre-vacuumed 
carts?)...
> 
> 
> > Thanks Jeff,
> >
> > Is this the case even if there's no ink in the tubing? The ink 
will
> > be pulled in and there shouldn't be problems with air bubbles?
> >
> > Thanks again,
> >
> > Jim Batzer
> >