Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "E Neilsen"
<e.neilsen2@...> wrote:
>
> John, If I am reading your post correctly, you are saying that as
the dyes
> mix together, that act, is causing them to fade. Any idea what they are
> doing? And are there tests that were done to predict this fade in
> relationship to amounts of  X amount of A + X amount of B fades at a
rate of
> Y? 

The destabilizing effects of dye mixtures and their respective dye
concentrations which leads to the commingling of the dyes alluded to
earlier is commonly referred to as "catalytic fading". For printers
that print gray with C, M, and Y blends, catalytic fading can often go
undetected in current industry light fade tests because those tests only
sample relatively pure C, M, and Y colors, plus "neutral grays" (no
matter how the grays are produced). Systems that make grays with heavy
GCR (replacement of C, M, and Y colorants with K in low chroma colors)
or substituted "photo gray inks" can pass such tests with much higher
scores than they deserve since the problem can still be manifested in
other color blends like blues, purples, reds, and skintone values. The
only way to account for catalytic fading correctly is to test a larger
population of colors laid down by the printer, especially important
color blends like skin tones,.

Swellable papers do significantly improve dye stability, but they do
not completely eliminate catalytic fading issues. An example of
catalytic fading on a swellable paper can be found here:

http://www.aardenburg-imaging.com/news.46.html

Note that the printer/ink/paper combination in this example was given
an industry rating of about 25 display years, but deserves less than a
10 year rating when darker colors, skintones, reds and purples are
evaluated as well, because severe catalytic fading is occurring when
the magenta and yellow inks appear in higher concentrations.

best regards,
Mark
http://www.aadenburg-imaging.com