Digital BW, The Print

Tyler wrote:

>...
>To my knowledge, MIS full quad inksets have not been tested by RIT.
>Let's assume for a moment that the lighter inks are
>dilutions of the black (is it the same black that was tested?).

Yes to both.

> As Wilhelm pointed out to the chagrin of many ink makers,
>diluting ink for light colors resulted in significantly shorter life.

I suspect this applies more to dyes than pigments.  As I understand the
process, oxidation is at the core.  The ratio of surface area to volume is
perhaps the main difference between the dyes and pigments when it comes to
oxidation and fading.  The pigments have relatively little surface area
exposed to the oxygen when compared to the dyes.  The dyes might be spread
even thinner when dilute.  The pigment particles stay the same size.

So, I'm no expert, but from what I've been told, I'd say there is a good
chance that the lighter pigments, to the extent they are merely the same
pigments spread out more, will fade at about the same rate as the full
strength pigments.

I might add that in my tests, the solid shades often fade faster than the
lighter ones.  I suspect this is because in the accelerated fading tests the
lighter tones absorb less energy and are at a slightly lower temperature
than the darker areas.

>This became an issue for Generations regarding how their M
>light and C light inks were made.

I'm not familiar with what they did.

Media Street claims 75 year Wilhelm for both its 4 and 6 color pigmented
inksets.  I believe these pigments are the same as the MIS pigments, except
for the black.  The standard MIS black and that used in the MIS
variable-tone inkset in my tests are much better than the Generations black
that is said to be at least 75 years in longevity.

> So the RIT results really may have
>nothing to do with how long an MIS quad print will last,

I think that these ratings have merit when compared to similar claims by
others.  So, the comparisons may prove very useful.

>and different coatings, which are evolving, can make a difference of
>decades (i.e. Liege vrs Royal Plush).

The paper used is clearly very important.

>Equally useful :), we get occassional reports from the Piezography
>people about their window tests.

Again, these types of tests may be useful if they are used in a comparison
context.  For my fade tests, I compare test strips that were in the fader at
the same time so that most of the other variables are the same.  If window
tests are done at different times and in different locations, I think I
would agree with your view that they show very little.

> Wilhelm has proven less than reliable too.
>All of these tests, yours, anyones, when
>acumulated are of value. But I don't see how anyone can
>make any definitive statements, some of them could be dead wrong
>because of methodology.

I agree.  The number of years of display seems especially speculative.

However, we can't just fly blind and hope.  So, rather than give up, I'm
trying to do what I can to find what works and what doesn't.  It may turn
out that my tests (even RIT's) were totally flawed, but at least I tried.

Paul
http://www.PaulRoark.com