From: Christina Z. Anderson (zphoto@montana.net)
Date: 04/23/03-09:08:33 AM Z
Good morning!
Well, Alberto and Katharine are proven right--yesterday I got my gum
and mixed 1+2 and 1+3 solutions. The 1+2 that Demachy and Henney and Dudley
used was volume wise exactly the same--in other words, 100g of gum mixed
into 200ml of water made a 300ml solution. Thus the 1:2 is a 33.3%
solution. Then 100g of gum into 300ml of water, which is the common form of
dilution nowadays it seems, is a 25% solution.
Next step, for you scientists/chemists: I have come across 4
preservatives to use in gum: the old way was mercuric chloride which in my
estimation is too toxic. Now I see thymol, formaldehyde, or sodium
benzoate. My question: is there a preservative any of you would recommend
over any other that is least toxic, least smelly, and does the job, and how
much to add? And is it true that formaldehyde does NOT harden gum arabic as
it does gelatin? Scientifically why not?
My sour gum works fine, btw. It smells a bit like sour milk.
Back to the dilutions. I know Demachy advocated the "feel" of the
solution as being the determining factor in gum printing. I'm using the
denser gum dilution to approximate that "feel" he might have had during his
day and also testing both dilutions side by side to see if there is any
advantage to using a thicker gum. More on that later.
In watching Livick's cdRom I notice that his layer of sensitizer is
quite poster paintish, thick, and opaque. He also says that if you cannot
get a fully tonal gum in 2 coats, you aren't mixing enough pigment into your
gum. Students love to hear that :) I have been doing mostly that lately,
but was wondering if most of you gum printers out there use whisper thin
layers that approximate water color washes moreso than the thicker layers
that cover the paper underneath.
I can't *wait* to get back into the rare books library this summer at
the U of Minn on my sentimental gum search. Hey, that'd be a great name for
a book...
Chris
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