BobWicks@aol.com
Date: 07/22/01-06:15:43 AM Z
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
simply this: there must be some organic ingredient to make the emulsion. The
bichromate sensitize and this organic mixture will form amino acid chains
when it is struck by light making it insoluble. I have a chemist colleague
who did original research on this if you are interested. My first attempts t
doing this, used simple gelatin that I got from the grocery store and it
worked fine. You really should look at David Scopics book The Gum Bichromate
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. The gum Arabic is not as sensitive to uneven application
as the gelatin is. 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.
Bob Wicks, Prof Emeritus, HACC
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