Re: Gum Tri-Color

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. 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.

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.

--
Bill Leigh
wrleigh@att.net
> 
> (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