Re: Commercial printing vs gum printing

I've been involved in both gum printing and conventional printing &
publishing for many years. I've read a lot of interesting comments in this
thread. I seriously hope nobody is considering unsubscribing due to this
discussion.

Here's a combination cyanotype/gum 3 color print I created from in -camera
color separations:
http://www.alternativephotography.com/artists/dave_rose/dr_fall_colors.html

>From my experience, it's possible to produce a decent black with tri-color
CMY gum printing.

Dave Rose,
Powell, WY

----- Original Message -----
From: <wrleigh@att.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, July 14, 2004 11:31 AM
Subject: Re: Commercial printing vs gum printing

> OK, Katherine, you win. I give up. I surrender. You are right. You are
always right.
>
> My initial reaction was to quote Dick Cheney, but I decided that wouldn't
do.
>
> Then I considered a long response, but I figured who really cared about
what I've had to say, so why bother.
>
> In the end, I decided that the information exchange here with the back
biting, criticism, and veiled insults were not worth it also.
>
> You can hold your own Saturday Night Live skit and "talk amongst
yourselves", but I won't hear it, as I'm unsubscribing.
>
> --
> Bill Leigh
> wrleigh@att.net
>
>
> > Hi All,
> > I've been too weary to read much of the intervening but am still
> > thinking about the stuff I went through so hurriedly the other day and
> > have a couple more comments:
> >
> > wrleigh@att.net wrote:
> > >
> > >I'm just saying that if you want Black or Neutral Gray, you can't get
>>there
> > by just CMY, you need to use Black or Neutral Gray.
> >
> > This just shows the fallacy of using a commercial printing model where
> > it's not relevant.
> >
> > The reason why you can't (or at least can't without a lot of monkeying
> > around) get a neutral grey or black in commercial printing without
> > adding black or neutral grey, has to do with impurities in printing
> > inks, as I quoted from the Photoshop manual the other day, not with any
> > discrepancy between color theory and reality as it relates to color
> > photographic methods.
> >
> > To quote another source, which unfortunately I didn't get the URL for
> > and can't find again, "The color gamut of process (CMYK) inks has always
> > been a problem. Poor purity of the cyan and magenta pigments is usually
> > to blame for the shortcomings in the CMYK color gamut. Cyan is typically
> > contaminated with yellow and magenta, for example, graying the color and
> > giving it a dull muddy appearance. The amount of contamination ranges
> > between 18-26% depending on brand and density. Magenta is contaminated
> > with yellow, if the pigment is rhodamine, and blue if the pigment is
> > rubine. It is common practice to mix them together to obtain a true
> > process magenta. While the hue may improve, the resulting mix will be
> > dull and muddy. ...Color printing inks also use extender pigments --
> > kaolin type clay."
> >
> > As near as I can determine, the most commonly used pigment for process
> > magenta is lithol rubine (PR 57) a pigment not used in watercolor
> > painting. The most commonly used process yellow is diarylide yellow (PY
> > 12) again not used in watercolor paints. The most commonly used pigment
> > for process cyan nowdays, also as far as I can determine, is pthalo, but
> > as explained above, both the cyan and the magenta contain significant
> > amounts of contaminants. I daresay economic factors preclude the use of
> > purer pigments, and all the "color science" that Bill refers to in
> > commercial printing is an effort to push inferior materials to do what
> > they really can't do very well. And I also daresay that adding black is
> > a much cheaper way to deal with the muddy colors than buying purer
> > pigments.
> >
> > We are not under these commercial constraints; we can buy very pure
> > pigments because we use small amounts, and furthermore the issues of
> > dot gain and trapping and out of gamut colors and all those things that
> > occupy printers are simply not issues that concern us.
> >
> > I'm getting to my point, which is that it may be more useful to think
> > of gum printing as a branch of painting than as a branch of commercial
> > printing, if we have to attach it to something other than itself.
> >
> > In painting, it is very easy to make a neutral grey or a neutral dark
> > that's quite black with three, or more commonly with two, colors.
> > Handprint lists a whole page of complements that mix to form a neutral
> > grey (chroma <2 as measured by spectrophotomoeter), and as a painter, I
> > never use black pigment or grey pigment but always make my neutrals by
> > mixing complements.
> >
> > For tricolor gum printing, of course, we use not complements but
> > primaries, but the three primaries used with intelligence can always
> > produce neutral greys and a dark enough neutral black to look black to
> > most reasonable people. Where a muddy brown results from the tricolor
> > mix, it's due IMO to the choice of pigments or possibly in some cases to
> > an imbalance in the pigment saturation among the three colors, not to
> > any great discrepancy between color theory and reality, a discrepancy
> > that simply doesn't exist in gum printing to the extent that it exists
> > in commercial printing.
> >
> > Katharine Thayer
> >
> > >
> > >
> > >
> > > --
> > > Bill Leigh
> > > wrleigh@att.net
> > >
> > > >
> > > >
> > > > On Wed, 7 Jul 2004 wrleigh@att.net wrote:
> > > > > ... Printer
> > > > > manuafacturers spend millions to get the proper combination of
colors to
> > > > > produce the proper results, and I find it extremely difficult to
believe
> > > > > that someone working in their basement (or wherever) combining
> > > > > approximate amounts of paints with unknown amounts of specific
pigments
> > > > > can achieve what the manuafacturers are unable to do with large
expense.
> > > > > Colo printing is quite analagous to gm printing, in that the
printer
> > > > > lays down 3 or 4 successive layers of colored ink or toner,
expecting
> > > > > the combination will!
> > > > > yield the desired effect.
> > > > >
> > > > > 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.
> > > >
> > > >
> > > > If we wanted color and effects identical to commercial materials,
why
> > > > wouldn't we just do C-prints or similar "color photography"?
> > > >
> > > > Judy
Received on Wed Jul 14 20:24:20 2004