Digital BW, The Print

I've been peaking on this GREAT newsgroup for 2 months now, learning 
a lot, and finally something I can probably contribute to. Part of my 
background is in flexo printing (the 50" web, 800 ft/min, 8-colors 
CMYK, $5 million dollar type of machines) as well as chemistry, 
amateur photograph and for 3 mths proud owner of a Canon S800 to get 
started in digital printing.

The inks we use in flexo printing are somewhat similar to the stuff 
used for inkjets (some solvent, water, carrier and pigments etc...). 
In my opinion, you certainly do NOT want to use the clear ink. It 
contains the carrier(or base) with the solvents but no pigments, and 
that carrier will dry and stick to the pad and to the printhead. Not 
good...

Jim, your comments were absolutely correct on acetone, water, 
solvents evaporating etc... Most solvents that dissolve the 
base/pigment combination (non-polar) do evaporate. Some that do not 
are oils (as in olive oil, kitchen oils or motor oil). But they do 
not have a good dissolving power, and if a liquid does not evaporate, 
I am fairly sure that there will be some sticking to the printhead 
and causing trouble printing.

Try to go for the solvents that do evaporate the slowest, and for 
that the glycols are the best option. Careful not to smell them too 
much though, some are toxic...

Hope this helped,
Erik.

PS: on a side question, is there anyone close to the Santa Monica 
(CA) Area that has a shop displaying quads? I am printing BW (and 
color) on my S800 using OEM (or MIS) dyes, on a variety of papers, 
and after MUCH MUCH work/adjustments am happy with the results (no 
metamerism that I can tell, no color cast except when on purpose, 
nice blacks,...). I would like to compare that with some true quads 
to see if it's worth converting...



--- In DigitalBlackandWhiteThePrint@y..., "jimhayes361" 
<jimhayes@j...> wrote:
> --- In DigitalBlackandWhiteThePrint@y..., Todd Flashner 
<tflash@e...> 
> wrote:
> > on 3/6/02 11:39 AM, jimhayes361 wrote:
> > 
> > > Therefore, a solvent that not only would dissolve
> > > clogs but not evaporate quickly or leave a harmful residue (say 
a
> > > perfume) on pad would be desirable.
> > 
> > I don't know if it fits the bill but I would think the clear ink 
> base that
> > both MIS and Mediastreet sell (I don't know what MIS calls 
theirs, 
> but
> > Mediastreet's is Jet Jrano) would be the safest thing.
> 
> You know, I WAS thinking of trying out some MIS clear base. I 
didn't 
> know it was Jrano, I thought that was more aggresive. Good point. I 
> was thinking someone could elaborate on the base stock to the MIS 
VM. 
> 
> > 
> > I also wonder how many of our clogs are really due more to air 
> blocks than
> > inks blocks. It's hard to know because they can take similar 
cures.
> 
> This is indeed the most frustrating thing about printers in 
general: 
> there's no way to isolate all the variables or find the exact 
culprit- 
> it hides behind at least two or three posible causes.
>  
>  Anyway, you know more 
> about
> > this than most of us so I'm really just asking.
> 
> 
> 
> When it comes to pig inks in a printhead, it's hocus-pocus. I had a 
> problem or two like this at HP handed me: the answer is test, test, 
> test, and statistics. That would be expensive for us to do, trying 
to 
> make our printers fail in numerous ways. I really have no answers. 
I 
> am trained to rake through comments made by others trying to 
eliminate 
> ambiguous or ill defined statements, and reformulate ideas to be 
> understood. And have others do it to me (with much better 
> alacrity<g>). If you work for HP R&D this happens every day you 
show 
> up- or it was the culture ten years ago. But I have no special 
> knowledge, other than what I picked up here and the usual sites and 
> people.
> 
> I'm at a loss with chemistry though, being a mechanical engineer, 
and 
> that ten years ago.
> Jim H
> 
>  
> > 
> > Todd