[alt-photo] Re: Gum Printing: Looking for some wisdom

Darkrooms, Department of Art darkroommanager at cornell.edu
Mon Mar 11 18:26:52 GMT 2013

Hello all,

I am reporting back with the tests I made last Friday.  I was going to mix
new Ammonium Dichromate, but I did not have a new bottle.  So, I decided
to retest my original test of Ammonium Dichromate.  You can view the tests
here: http://www.flickr.com/photos/93779173@N03/sets/72157632974249458/

I think that I now have a good jumping off point with these tests.  This
week I hope to work on the calibration of the QuadTone Rip negative.

Thank you for your help!
Jennifer Gioffre
Teaching Support Specialist

Architecture Art and Planning
Cornell University
120 Tjaden Hall
Ithaca, NY 14853
Office: 607-255-4207
Fax: 607-255-3462
jmg393 at cornell.edu
darkroommanager at cornell.edu

On 3/7/13 1:56 PM, "Kees Brandenburg" <workshops at polychrome.nl> wrote:

>Hi Jennifer,
>As we are talking about gum, let's not forget this variable. What gum
>arabic do you use? Premixed or self mixed, and at what concentration and
>baumé? I'm using a 14-14,5 baumé self mixed gum. This is about 26-26,5%
>Looking at your exposure times for cyano and van dyke, compared to mine
>(6 and 4min) I would say that you would end up somewhere around 10
>minutes with your bank of UV and normal gum sensitivity. I find your
>pigment concentration rather low. With 'normal' strenght gum I am using 1
>gram per 20ml gum for winsor blue and lamp black on gelitin/glut sized
>paper and never see any stain.
>With dichromate I'm a 'replenisher'. When the bottle seems to empty with
>a coming workshop or project, I make some new and fill the bottle up.
>From time to time it stands for several weeks or more.
>Alt-photo-process-list | http://altphotolist.org/listinfo

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