Digital BW, The Print

Jim,

I am not aware of another alternative process using gum that does not use either potassium dichromate or ammonium dichromate.  Most people prefer ammonium dichromate because it produces a longer scale.

As far as toxicity, the dichromates are toxic, no doubt about it, but can be easily used at home with reasonable care.  The only mixing you do is create a saturated solution with distilled water, so you can transfer the powder outside on a still day and be fine.  Other than that, use rubber gloves when developing the prints.  There are hundreds of people doing gum bichromate prints at home without a problem.  It is a beautiful process.

Here are some good resources:

http://unblinkingeye.com/Articles/3CG/3cg.html
an article by a friend of mine, Sam Wang, a master of this process

Christina Z. Anderson
website of another friend who has a great book Alternative Processes Condensed—this has a great section on Gum Bichromate.  Christina will be publishing the definitive book on Gum Bichromate later this year. 

Hope this is helpful

Mark Nelson
Precision Digital Negatives
PDN Print Forum @ Yahoo! Groups
Mark Nelson Photography


On Sep 13, 2008, at 8:27:07 PM, geoman4919 <geoman4919@...> wrote:
From:   geoman4919 <geoman4919@...>
Subject:    [Digital BW] gum arabic printing question
Date:   September 13, 2008 8:27:07 PM CDT
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Hi, I am interested in gum arabic printing. This method of printing a
negative uses gum arabic and a watercolor pigment, with a sensitizer-
potassium dichromate. The dichromate renders the gum arabic insoluble
in water on exposure to light. The print is developed in warm water.
The unexposed portions of the print dissolve. I want to find another
chemical rather than the dichromate to use. This chemical is too toxic
for home use and a substitute is needed. Does anyone know of another
chemical which will release oxygen on exposure to light like the
dichromate? Alternatively, a chemical that would produce acidic
conditions on exposure to light would also render the gum arabic
insoluble.

Best Regards

Jim





--
Best Wishes,

Mark Nelson
Precision Digital Negatives
PDN Print Forum @ Yahoo! Groups
Mark Nelson Photography


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