>If doing gum Printing it is my opinion that the yellow layer first is best,
>because the yellow pigments usually have white in them for some reason, and
>this white will change the way all previous layers appear.
>
This reminds me of a 3-color gravure lecture/demo I gave some years
ago. I was assured that the intaglio lab I would be using had all of
the process colors available, so I didn't bring my own inks (bet you
can guess the moral of this story). Turns out that they had the process
blue (cyan) and process red (magenta) but no process yellow. Looking
over the selection, I picked a cadmium yellow ink that visually was
very close to process yellow. I even added lots of plate oil for
transparency and compensated with extra carbonate for the "right"
stiffness. I figured the color balance would be off a little, but close
enough for the demo.
The yellow printer inked well and everything went fine printing the
first two layers, but when it came time to peel back the paper after
the third run through the press, the point at which there are usually
oohs and ahhs from the audience as they see the full color image
finally revealed, there was just a disgusting yellow layer opaquely
covering the rest of the image.
What I am leading up to is that I wonder if it would be worthwhile
looking at some different options for yellow pigment than the one you
are using and finding necessary to print first. I realize that you must
have already done some searching for the right yellow pigment. No one
who makes 3-color gums hasn't already "suffered" enough. I also realize
that there aren't any standards for process colors for gum printers the
way there are in the ink processes, so you may never find the right
yellow. Still, with the wide number of choices for watercolor and
guache pigments out there I have to believe that there must be one that
offers the right amount of transparency to use on top of the other
colors. It doesn't seem like a satisfactory process color equivalent if
it doesn't work unless it is printed first.
Of course, if you like the way it is working for you, then you also
have to consider the "if it ain't broke, don't fix it" factor.
Just a thought,
Carson Graves
carson@ileaf.com