From: Gary Nored (gnored@centurytel.net)
Date: 10/03/03-07:34:51 PM Z
On 29 Sep 2003, at 15:49, Katharine Thayer wrote:
> Hypothesis:
> The addition of dichromate to the pigment and gum makes no
> difference in staining.
>
I'm way behind in my reading lately, but I tried a gum
"test" or two today to see if I could make any progress in
my gum woes. I hadn't read this anywhere -- it just
seemed like a reasonable thing to try.
I coated one sheet of Fab. Uno, unsized, with
gum+pigment on one endand gum+pigment+dichromate
on the other.
I coated a second sheet the same way, but this one I had
previously sized with a 1:4 water to Liquitex Gesso
solution.
I used Windsor and Newton Lamp Black Series 1AA,
#0102 327 for the pigment.
I then covered a center strip of each and exposed them to
the bright Texas sun for 3 minutes, and washed in
distilled water. Here's what I observed.
The staining (I'm just guessing here -- that's the color left
in the completely unexposed areas which should,
theoretically, wash off, right?) is the same, dichromate or
no dichromate. The gesso sizing makes the staining a
little worse.
I wasn't trying to conduct the infamous staining test -- I
was actually just trying to see if using distilled water
made any difference here (it does). My purpose in mixing
pigment and gum was just to see if it all the gum/pigment
washed off (it doesn't seem to). But FWIW, it appears to
me that, at least in this kitchen, adding dichromate has
no effect on how cleanly the gum washes off Fabriano
Uno.
Now I'm wondering why it doesn't. Maybe I'm not getting
the pigment completely dissolved in the gum. Should I let
the gum/pigment mixture set up for awhile?
Gary Nored
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