From: Judy Seigel (jseigel@panix.com)
Date: 07/22/01-03:34:02 PM Z
On Sun, 22 Jul 2001 BobWicks@aol.com wrote:
> Judy:
> I use Gum Arabic (14 degree Baume) that I purchased from a graphics printer
> and it works marvelously well. Most of these products used in plate making
> have a preservative in them, but you must check it out to be sure. I have
> been doing this for 30 years. I think it would be a lot easier fori you than
> using the starch that you are using. The principle that makes this work is
You seem to be confusing my question about starch as *size* wih its use as
colloid. I'm not using starch for anything -- though I am lover of many
gums (more than I can comfortably store -- stop by & I'll share) and I
harbor gelatins from much of the animal world, Peter Rabbit to Miss Piggy,
& have written probably too much about both (here & in Post-Factory).
A while back I did test a few starch sizes, but haven't yet found a good
one -- and since the gelatin size is incompatible with some other elements
I want to use -- inquired about Heidi's.
> ... You really should look at David Scopics book The Gum Bichromate
I did...
> Book, available at Light Impressions of Rochester, NY. He describes the use
> of Gum Arabic for gum printing, mixed with Winsor Newton Water colors for
> archival results.
I had a lot of problems with the Scopick book: too many errors & omissions
-- as I've also explained probably too many times on this list... (For
instance, have you tried his so-called plasticizing gum for dry pigments?
A fallacy based on a fallacy, taken from Mayer's Artist's Handbook where
it's given for a different purpose. It stains more in gum printing than
you'd think humanly possible.) Etc.
> ..The gum Arabic is not as sensitive to uneven application
> as the gelatin is.
I don't follow you here. You mean uneven as a size or a colloid? Gelatin
vat-applied is sufficiently even. I've not heard of uneveness as a problem
even with brush application (which many use but I do not advocate except
for touch-ups), though it's a possibility.
Gum can of course be used as size, hardened with dichromate and exposed
without pigment, but that's got problems of its own, particularly a
tendency to discolor -- & overall more trouble than proper vat sizing.
> ...Since gum printing does not give a very long tonal scale,
> I have used Cyanotype in combination with gum printing to give a nice rich
> tonal result.
Printing fake "real color" from one neg, as I am, the cyanotype, which
cannot be brushed off, doesn't work unless you make a separate negative &
possibly not even then, as I noted at 4 AM a couple of days ago. If you
make flat negatives with all the info you can get adequate scale in one
coat of gum tho several coats of different densities from a longer-range
negative work better.
Also, as Lukas Werth points out in his marvelous article on casein
printing in current Post-Factory (#6), you can use casein, a process
related to gum printing, for your longer-scale (ie, platinum !!!!)
negatives. Actually, I haven't tested that yet, and, as I said in an
editor's note I am willing & ready to believe that other variables affect
the scale, not just the colloid. But re-reading his article this AM (I'm
working on the index, working on it, really) I'm struck again with its
charm. Perfect combo of personal & philosophical with the innovative &
technical (which this may not be, sorry). As Lukas suggests, the reason
for greater popularity of gum is probably not "any inferior qualities" of
the casein, "but historical coincidence and the lines of communication
among photographic artists at the end of the 19th century."
Which is to say, pre-Internet.
PS. Lukas, I plan to try the casein this week... just gotta get to Kremer
to get some.
cheers,
Judy
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| Judy Seigel, Editor >
| World Journal of Post-Factory Photography > "HOW-TO and WHY"
| info@post-factory.org >
| <http://rmp.opusis.com/postfactory/postfactory.html>
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