Digital BW, The Print

The HP Z-series of printers has a built-in ink agitation system. The
base of the cart has a soft "rubber bung" that is periodically
agitated by the printer. This serves to help keep the pigments in
suspension.

Also, since the printer has a built-in Spectro, it prompts you to
"recalibrate" your media periodically. This is not to be confused with
making a new profile. (which the printer also can do)

With these two capabilities with in the printer and the "relatively
small" ink carts (130 ml), I have yet to notice any deviance in
printing results in the 9 months I have used the printer. Of course
Ernst has been using his for over 2 years now.

It is my understanding that thermal inks have a slightly less viscious
consistency compared with piezo inks. Hopefully in mixing with a piezo
base during dilution, and the inherently more "forgiving" nature of
the piezo print head, printing characteristics of the diluted inks
should be satisfactory. But of course use of a base different from
HP's might explain why Paul is seeing some settling of his dilutions.
HP ink has quite a "unique" odor, due to the co-solvents and glycols
they employ.

John Nollendorfs

   
--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "pr_roark"
<pr_roark@...> wrote:
>
> Tony Sleep <TonySleep@> wrote:
> 
> > On 24/01/2009 pr_roark wrote: ...
> > > The most surprising result of the test is that the HP 
> > > Grey settled significantly more than my dilutions of the HP PK.
>  
> > HP claim their electrostatic encapsulation of pigment 
> > maintains dispersion and prevents settling.
> 
> All inkjet pigments have some form of stabilization coating, even if 
> just an un-attached surfactant.  These stop 
> flocculation/agglomeration, but the carbon-based pigments are still 
> heavier than water or the base/medium that is likely used.  Brownian 
> motion will help and may be enough to keep the very smallest 
> particles from settling, but from what I can tell, all of our 
> pigmented inks have particles that will ultimately settle or separate 
> if not agitated.  The higher the viscosity of the medium or dilutant, 
> the slower they settle.  Specific gravity of the medium is also a 
> factor.  However, the bottom line is that even with an outstanding 
> stabilization coating, our pigments are still subject to settlement 
> or stratification (particularly multi-pigment mixes) in the medium if 
> left still for long enough.
> 
> So, while I think HP has an excellent stabilization system, I doubt 
> that by itself is enough.  My tests indicate their grey ink likely 
> settles with time.  It appears, however, that HP has taken steps to 
> deal with that issue.  I certainly would not worry about it if you 
> have or are considering buying an HP printer.