Re: Gum variables
Sam Wang (stwang@CLEMSON.EDU)
Wed, 10 Jun 1998 13:21:05 -0400
>This is very interesting! I thought about doing things like this too, but I
>haven't done it yet. This is more like watercolorist or painters' approach. I
>also do Chinese brush painting. The way I see it is one can train his/her eye
>so that s/he can make judgement from the mixture directly. (In painting, I can
>mix the ink and judge the darkness and even gradation while it is on the
>palette and *know* how it will look when absorbed on sumie paper and then
>dried. It seems to me then one should be able to do such a judgement with gum
>mix too). But I figure those (including myself at this stage) with less
>experience will desire to have some control using fixed formula.
>
>>> THEN add enough dichromate in powder form to the mixture.
>
>How do you determine the amount of dichromate? Do you determine by the volume
>of your mix?
Dave,
I don't do watercolor painting, but I mix the gum with pigment till it
looks "right", which is important because colors for a particular image may
need to be different from another - we are not talking about objective
color reproductions here.
Franklin Enos showed me his measuring "spoon" - a piece of 1/4" aluminum
with a 1/4" hole drilled through it, with one end blocked off. I copied it
in acrylic, and one "spoonful" with this is just enough to sensitize 10 cc
of gum.
When I was doing silkscreen, I used the same measure for the gelatin emulsion.
What kind of light are you using for gum? My gum/ammonium dichromate
exposures run between 1-1/2 to 3 minutes in the NUARC, and that's fast
enough!
Sam