Digital BW, The Print

Paul Roark wrote:

> Bruce wrote:
>
> > The main disadvantage is the possibility of
> > differential fading over time pushing the print's tone warmer or cooler
> > than you intended.
>
> No, there should be no significant difference here.  I believe the K7 inks
> have differing amounts of color pigments mixed in.  I may be wrong 
> here, but
> I simply don't know of any pure carbon pigments that can print neutral 
> over
> the entire range of densities we're interested in.  It'll really take
> controlled, comparative fade testing to see what, if any, aging 
> differences
> there are from these inksets.  The differential fading problem occurs with
> color inksets that attempt to make a gray tone from color inks.
>
> A "neutral" tone that is composed of predominantly carbon will usually 
> have
> some color pigments mixed in.  These will fade faster than the carbon, but
> the carbon also shifts color.  So, there will be color change in either
> case.  What usually dominates in a reasonable time span (like one's 
> expected
> life span for normal display conditions) is the warming of the 
> carbon.  (If
> you're using brightened paper, the burning out of the optical brighteners
> may be the largest change -- which is a big reason I prefer paper with no
> OBAs.)

First, I don't know the compositions of the various inks. I don't see 
anything on the InkJetMall site that uses the words "carbon pigment" 
however. I'm not even sure I now how a carbon pigment ink differs from a 
pigment ink. Probably in the amount of carbon, but I have no idea where 
that line is drawn.

Second, I didn't say there would be any differential fading. I said 
there was a possibility of differential fading. It stands to reason that 
the possibility of differential fading would be greater for the inkset 
with the most color pigments. And a variable tone inkset is going to 
have to have more color pigments than a fixed tone inkset. It's the 
color pigments that provide the "variable" in the variable tone inkset 
after all.

That doesn't mean that the variable tone inkset will exhibit 
differential fading. That the possibility is greater doesn't mean that 
the actual amount of differential fading will be noticeable or 
objectionable.
--
Bruce Watson