Digital BW, The Print

> Our inks are tested to an internationally accepted standard
> the Blue Wool Scale (BWS).

I just want to comment a bit on the Blue Wool standard.  It has been used by
many industries for quite a while, but the Blue Wool test does not appear to
be the internationally accepted standard for photos or inkjet pigments.

Let me quote Lyson:

"Lyson has a number of methods for observing pictorial image fading of which
Blue Wool and simple window placement are still carried out. However, the
test that we believe gives the most accurate prediction of actual indoor
display life is the method used by Wilhelm Imaging Research, Inc
(www.wilhelm-research.com). The Wilhelm test criteria has, in the main, been
adopted into the 1996 ANSI (American National Standards Institute) document
'Stability of Colour Pictorial Images', which itself is in the process of
being furthered into an ISO standard. By definition, this will become the
International test that our industry should orientate itself to."
http://www.nazdar.com/Lyson/lyson-longevity.html 


I actually have the Blue Wool test materials and decided not to bother with
them.  I'm not saying they are not relevant, but they do not give enough
information to distinguish the inks, and testing to the end stage is not
what I'm most interested in and is not practical for me.  I do not have the
time to do that for enough inks and papers to allow me to move forward at
the speed this industry moves.

Let's look at some actual numbers and equivalences.  The Blue Wool rating of
7 is 300 megalux hours of exposure before fading becomes noticeable.  (See,
for example, http://www.handprint.com/HP/WCL/pigmt6.html#lightfast)  This
translates into 152 Wilhelm years of display.  (Wilhelm uses 450 lux for 12
hours per day.)  The Blue Wool rating of 8 (the highest) is 900 megalux
hours of exposure before fading becomes noticeable.  This is 457 Wilhelm
years of display.  

Most of the action with respect to the pigments I'm working with is between
the BW 7 and 8 ratings.  That is rather large gap -- from 152 to 457 Wilhelm
years of display.

It also would simply take me too long to test to the end points, and I don't
think that is my main interest anyway.  So, I test for shorter periods, but
long enough that the initial high non-linearity I've found with some inks
does not overwhelm the final results.  (Most of this is in the first
"Wilhelm" year.)  

As an example, in one test a bit more than a year ago, I exposed samples for
what would be the equivalent of 13 Wilhelm years.  In this test the MIS UT7
did 2.8 times better (looking at the change in Lab L) than the K3 B&W inks
on Premier Art Hot Press (the same coating as UltraSmooth).  Wilhelm rates
the K3 B&W inks at ">205" years on UltraSmooth under glass (not UV glass).
So, could the UT7 inks really "last" 574 years in typical indoor display?  I
don't know, and I'm not going to do the testing needed to get to that stage.
That would, by the way, be a Blue Wool rating of 8.  In fact, Livick did a
test on coated UT inks all the way out to the end point.  He came up with a
rating of 681 years. 

Any accelerated test is subject to criticism.  They all introduce factors
that might skew the results one way or the other.  But when I see most of
the industry going to Wilhelm, that makes his procedures the de facto
standards regardless of their merits.  In fact, however, my reading and
experience suggests Wilhelm is the best there is.

At any rate, I simply want to point out that Blue Wool rating of 7 is fine,
but it does not tell me what I'm looking for.  It does not tell me these new
inks are any different than the others that are out there.

I'd love to see a comparative test. I really hope you do have something
special.  

Epson's Claria "dye" inks demonstrate rather convincingly that significant
progress is possible and perhaps likely in this field.  The pigments we use
are called "dye stacks."  I wonder what happens when Epson "stacks" the
Claria dyes?  Would there be a huge (like 4x) improvement in the pigment
lightfastness the way there appears to be for the dyes in their soluble
form?  Would we be looking at color prints with "800 years" of display life?

Paul
www.PaulRoark.com