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

[Kees Brandenburg]

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.

kees