Digital BW, The Print

Paul, Jerry,

Jon has said there are dyes in Piezo to achieve the desired tone. He 
did not clarify their nature or amount other than that it was small.

I think that Paul's test is very interesting. First the color of the 
Piezo ink is the colorcast I see in all Piezo prints under tungsten 
or halogen lighting. The amount of green I see in the prints is very 
slight. (I may be colorblind, as no one else seems to see this.) I 
see it as soon as it comes out of the printer. It isn't something 
that happens later. In daylight I don't see the green cast and the 
Piezo looks just fine with a warm-neutral tone.

I don't see this in the MIS VM prints that Todd sent me and only see 
it in the warm area of a split tone print I received in the print 
exchange from Ron Landucci that was done with the MIS VM inks.

I believe this is counter to what Steve reported recently that the 
MIS prints looked greener than Piezo prints in daylight, so perhaps I 
am color blind after all. Or if both MIS and Piezo have metamerism 
perhaps it is in the opposite directions.

Secondly Paul's test indicates to me that the MIS ink is a more 
stable dispersion. The pigment and particles appear to stay together 
rather than separating. This may explain why there are no clog 
complaints about the MIS inks and clogging is a way of life with 
Piezo. Paul can you send me a higher resolution copy of that image 
file? I would like to see if there is any solvent spread from the MIS 
ink.

There was the one report of a Piezo print on EAM displayed in an 
elevator where both the paper and the ink turned green. Jon blamed 
this on ozone in the environment. Obviously something happened to the 
print but I doubt that it was ozone. Bob Meyer has been investigating 
the relation between the 1270 Epson ink failure and ozone. Todd is 
sending him two Piezo prints I made on EAM, one coated and one 
uncoated, to put in his ozone chamber so we should have an answer in 
a few weeks. I also offered to coat some color prints for Bob and he 
requested that I not use EAM, as this was very stable with the 1270 
inks. He did not mention any problem with the paper turning green due 
to ozone exposure.

I think there are two issues with EAM and Jerry has already reported 
one. In window testing the paper yellows a bit. This fits with what 
Robert Rex of Crane posted about optical brightener agents. They have 
a fixed life and then fade leaving the paper more yellow than it 
started out. Second it really does test out acid so it may not last 
as long as non-acid papers. How critical either of these are, is up 
to the individual user.

How many green issues there are? There are:

- Piezo printing starts producing tonally degraded prints and a shift 
to green on some printers as the heads slowly clog up. The Jim Hayes 
issue.

- Some piezo prints on EAM have turned green sometime after they were 
printed.

- A couple of people have said that EAM's base color looks slightly 
green to them from the optical brighteners.

- Ozone reportedly turns EAM or Piezo on EAM green.

- I see a green shift metamerism in tungsten light with Piezo on a 
wide range of papers.

Are there others I have left out? It is really confusing because 
people keep talking about the green problem but don't say which one.

Martin

--- In DigitalBlackandWhiteThePrint@y..., "Paul Roark" 
<paul.roark@v...> wrote:
> Jerry,
> 
> You wrote:
> 
> >Paul, hasn't Cone repeatedly stated his inks are pure pigment?
> >I thought he had.
> 
> I thought his position was that there had to be some dyes in the 
pigmented
> inks to give them proper color.  For example, the carbon black is 
said to be
> brown with if no "dyes" are added.  I think that MIS or Media Street
> originally came out with a black ink that was pure carbon, and it 
was not
> well received -- too warm and not dark enough.
> 
> MIS has also stated that their inks contain about .5% "dye."  
However, MIS
> characterizes the "dye" in their inks as the colorant that coats 
the carbon
> particle, which is the core of the pigment particle.  I have gotten 
the
> impression that all these desktop pigments are carbon particles at 
the
> center.  Even the color pigments apparently are carbon coated with a
> colorant -- which MIS calls a "dye."  (Note, this is contrary to my
> understanding that "dye" usually means in this industry a colorant 
that is
> dissolved in the solution as opposed to a pigment particle that is 
merely in
> suspension -- and hopefully kept there by the Brownian motion of 
the fluid
> base.)
> 
> My understanding from MIS is that the coating on the carbon 
particle is the
> only "dye" in their inks.  This is unlike some "pigmented" inks 
from other
> companies, however, where there are also dyes added to the mix in 
addition
> to the colorant/coating that is on the particle.  In these inks, 
the dye
> would be dissolved into the solution, not a separate particle in 
suspension.
> I suspect that Piezo is in this category, and that is why we see the
> separation in the chromatography experiment.
> 
> However, I, again, am not a chemist and could be totally wrong on 
how these
> inks are made.
> 
> Paul
> http://www.PaulRoark.com
> 
(snip)