Re: Gum Tri-Color

From: Katharine Thayer ^lt;[email protected]>
Date: 07/11/04-03:44:07 PM Z
Message-id: <> wrote:
With all due respect to Katherine, the issue is not "computer printers
and inks or commercial printing presses and inks", it is color science,
which is concerned with
the ability of pigments, dyes or inks, when combined in some particular
ratio, to create the proper colors, including absorbing ALL of the light
which is directed at the
print, resulting in a solid black. In theory, a pure cyan, magenta, and
yellow combination will result in black, but not in fact.

Well, all I know is color photography and gum printing. In color
photography only three color layers are required to make black in a
color photoprint, and in gum printing only three colors are required to
make a solid black. You can argue til the cows come home, but your
arguments aren't convincing. Mechanical devices and their respective
inks are not the same as color photographic printing processes, and
trying to equate them just confuses people.

To quote the Photoshop manual, "In theory, equal parts of cyan, magenta
and yellow combine to subtract all light reflected from the paper and
create black. Due to impurities present in all printing inks, however, a
mix of these colors instead yields a muddy brown. To compensate for this
deficiency, printers remove some cyan, magenta and yellow and add

This is an issue for mechanical printing devices and their respective
inks, but not an issue that relates to my process, as I keep saying.

> Please post 2 instances of the same print, one of which was printed with lampblack and one with some combination of your choice of cyan, magenta, and yellow, which show that the color is identical. Also try scanning the print and see what Photoshop says is in each of the CMYK channels.

Hmm, are you planning to pay me for my time to do this? If not, I don't
see that I have any obligation to obey this order. If it looks solid
black to me, that's good enough for me.

> Note that on a color monitor, which is an RGB device, the black is mapped to an absence of each of R, G and B, so a color monitor to display the difference may not really be an accurate way to view the difference.

???? I'm looking at the print when I say it's solid black, not at an
image of it on the monitor.


> --
> Bill Leigh
> >
> > (2) With all due respect to Bill Leigh, we're talking about color
> > photography and pigments here, not computer printers and inks or
> > commercial printing presses and inks, which have requirements and
> > problems and characteristics that have nothing to do with what we're
> > talking about. One of the sources of confusion that sometimes arise here
> > is when people get gum printing confused with commercial printing. They
> > have very little in common, as far as I'm concerned. And yes, in my gum
> > printing world, as in the world of other photographic tricolor
> > processes, three saturated primaries do produce a solid black.
> >
> > Katharine Thayer
Received on Sun Jul 11 22:40:10 2004

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