Re: Gum Tri-Color

I'm inclined to think, on reflection, that in spite of the fact that the
magenta inks for commercial printing have a reflectance curve with a
secondary peak more in the blue-violet than in the violet range, and
that most of the pigments that are used for magenta in tricolor gum have
a secondary peak more in the violet range than the blue-violet range,
that the match of the reflectance curve to magenta printing inks isn't
the crucial variable in determining whether the pigment chosen for
magenta in tricolor gum is a good magenta or not.

I think that whether the peak is over into violet matters much less than
how broadly it extends into the blue region. In other words, I'm saying
(1) that choosing a pigment that matches the reflectance range of
magenta ink for the printing process might not be a useful thing to do.
Since I've never thought that tricolor gum had much to do with
four-color printing anyway, I guess I shouldn't be surprised by this
realization, but I am a bit.

(2) that I think it's the extra blue in some of the pigments used for
magenta that causes the brown tones. I suspect, for example, that it's
the blue-violet in the PV19, reflected in the broad secondary peak that
extends across the blue, that makes it give the brown tones when mixed
with yellow and blue. Alizarin crimson and PR209 (quinacridone red)
have very little reflectance in blue, but slight upticks in violet, and
I think that's why they are better pigments for tricolor (as far as hue)
than PV19.

I suspected this before, but my suspicion was corroborated by an insight
from handprint.com, which recommends quinacridone magenta (PR 122) as
the best "primary magenta" for mixing bright violets, but adds that
unfortunately there is so much blue in it that it "produces rather dull
brown or tan mixtures when mixed with orange or yellow." This pigment,
which I wouldn't recommend anyway because it gets mixed reviews on
lightfastness, has a very high and broad secondary peak, peaking in
violet but staying high across blue and cyan and even into green. I'm
not going to buy this pigment, but I would be willing to bet that it
would print very poorly as the magenta in tricolor gum. It is bluer in
printed swatches than PV19(gamma), about halfway between PV19 gamma and
PV19 beta, which is distinctly blue-violet; I'm surprised that anyone
recommends it as a process magenta (Winsor & Newton's "Permanent
Magenta" that was one of the recommendations I quoted from someone's
manual earlier, is this beta PV19.)
Katharine
Received on Sat Jul 3 17:12:17 2004