Digital BW, The Print

>... In discussing these issues with a Cone 
> representative this morning, he informed me that 
> the K3/VFA/USFA figures I report are because Epson is using 
> dyes in these inks.

I do not think the Epson UC K2 or K3 inks have dyes in them, at least in the
meaning of the term as it is usually used.  The comment above about the
numbers presumably is about the dmax.  Epson matte black in the k3 printers
gets an outstanding dmax on some papers, and not so great on others.  It
appears to be not only because of the quality of the ink, but also because
Epson has done an excellent job of matching the printer's characteristics --
dither and ink loading -- to the papers Epson thinks are most important.  

In fade testing the Epson MK, like MIS's Eboni, did very well.  If I wanted
the most lightfast print possible, regardless of smoothness or tone, a black
only print using one of these inks would probably be the route I'd take.  

The hybrid pigment-dye blacks are obvious in fade testing.  They go through
a fast initial fade.  Then when the dyes burn off, they settle into a slower
fade rate for a long time.  Neither Epsom MK or Eboni show that fade
pattern.  In fact, both become a hair more dense at first.  Ironically, the
original Epson "Archival" black did act like a hybrid ink in fade testing.

The K3 "carbon" core pigments are actually about half carbon and half
"proprietary pigments and dyes."  (I think that is the catch phrase Epson
uses on its MSDSs.)  But, this phrase does not mean that there are dyes in
solution.   The color pigments we use are often referred to as "dye stacks."
They are often chemically the same as the dyes, but they do not dissolve in
the water base like the dyes that fade fast.  The dye stacks are solids in
suspension; they're legitimate pigments.  With respect to the carbon, I'm
not sure what Epson is doing.  Lots of the action is at the edges of the
graphite plates.  That is about the only place that form of carbon has any
open bonds, and they are used by the companies to give the pigments
favorable characteristics, like staying in suspension and not aggregating.

>The problem with using color inks to make B&W prints ... is 
>that the color inks can introduce problems like subtle color
> casts, color shifting from dark to light, and color 
> casts due to differential fading ...

Yes, which is why I always want the least amount of color and the most
carbon.  However, carbon is too warm for me in most instances.  So, the use
of some color pigments is necessary to get the tones I prefer.  Among the
color pigments, cyan is about the most lightfast.  I don't worry about if
fading from light, although air pollution might be a problem.  The magenta
is more of a concern.  I specified the MIS R800 Blue clone pigment in the
MIS mixes because it is more lightfast and stays in suspension better.  In
my new 7500 setup I'm using Epson UC LM.  I have some tests that suggest it
is very good.

C. David Tobie noted: 

>The quantity of color ink used in the latest "two gray" printer's 
>drivers is minimal, and the pigment inks involved are very stable. 
>So both illuminant metamerism and color shift over time are also 
>very minimal. ...

To give some quantification of this, in the IJC curves used in my new 7500
setup, the highest ink load I use is 22 for the LK.  The LM and LC (at 50%
dilution) have ink loads of 3.

I sometimes wish we had a totally neutral, pure carbon, but as far as I can
tell, no one has developed one yet.  Some of the black inks will print cool
when they are applied in high loads, but in the midtones and when diluted,
they all are still warm as far as I know.  The k3 LK and LLK are less warm
than the MIS versions, but I think they're too green.  In most respects I
like the warmth of the MIS carbon.  It allows that ink to be used as a
low-gamut yellow in a CMY color space, and I like the ability to profile my
papers or choice to the tones I want.  The MIS carbon, LM and LC combination
gives me what I want from a B&W inkset.

Paul
www.PaulRoark.com