From: Keith Gerling (kgerling@ameritech.net)
Date: 05/10/01-07:55:56 AM Z
Hi Lukas,
1) Surprisingly, I have no problem with the dichromate bleaching the
kallitype. Well, actually, very little, but I'll get to that. Printing gum
over kallitype is no easy matter for me: all of the necessary factors have
to be in place for both of the processes to work, which is not always easy.
For my process, this means shrinking (and "un-sizing") the paper, exposing,
processing and washing the kallitype. The print is then sized with gelatin
and hardened in glyoxal. Perhaps because the silver has imbedded itself in
the paper, or maybe because of the sizing, the dichromate seems to have no
effect on the kallitype image. The only exception to this is in cases where
many coats of gum emulsion are applied, say 6 or more. Because I am very
conscientious about proper disposal of the dichromate waste, I often let the
first gum wash bath become very concentrated with dichromate. The print, in
effect, is exposed to hours of soaking in a dichomate bath! Still, the
bleaching, in these cases, is in the order of about 5%. Often times, I find
this works to my favor, as the multiple gum coats tend to build densities
and the print can actually benefit from a little bleaching.
2) The majority of my work is with digitally prepared negatives. I use
Adobe Photoshop, and when preparing the negative separations, I am careful
not to allow the densities to "close" up. There are many ways to do this,
but I have found that just using the Photoshop packaged Duotone settings can
be a pretty good place to start. The Duotone function is intended to be
used with ink printing, which is subject to the same shadow build-up
concerns. For those familiar with Photoshop, the Curves for the separate
negatives are adjusted in such a way that they complement each other. For
instance, the Shadow Negative can be flat in the lower ranges and steep in
the midtones and highlight regions, while the Midtone Negative can be flat
in the middle region and drop off at the extremes, etc.
I hope this helps.
Keith
-----Original Message-----
From: Lukas Werth [mailto:lukas.werth@rz.hu-berlin.de]
Sent: Thursday, May 10, 2001 5:52 AM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: gum over platinum and the like
At 18:36 09.05.01 -0500, you wrote:
>I frequently print gum over platinum (as well as kallitype and palladium).
>I have two approaches:
>
>1) In printing from a B&W negative, I'll print about 90% of the image in
>metal. Gum is used to enhance the print in subtle ways, similar to a
>"duotone" or "tritone" mode in Photoshop. Fascinating effects can
sometimes
>be gained with using very small amounts of contrasting colors such as green
>and red, each layer printed with a separate negative.
>
>2) Printing with gum, I sometimes use a metal for the black component in a
>CMYK process. The platinum or kallitype adds "punch" to the picture, but
in
>this instance, takes a back seat to the colors of the gum.
>
I first have a technical question here: does the kallitype not get
partially bleached by the dichromate? I tried to print over a salt print,
and this is what happened - I printed the salt print on the already sized
and hardened paper, though.
And, if you print with gum over platinum, do you close shadows, or do you
take care they remain open?
What do you mean with "separate negative": digital, I presume (?), but
different in which ways?
Lukas
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