From: Katharine Thayer (kthayer@pacifier.com)
Date: 02/04/00-01:57:46 AM Z
Funny, we had this very discussion just a few weeks ago in a thread
labeled "Acrylics in Gum Dichromate" where it seemed that those "gum
printers' who have successfully used acrylics for pigment and size are
actually GLOY printers, but those who use the traditional gum method
using gum arabic do not find acrylic to give good results either as a
pigment or as a size.
In that thread I suggested that the two substances are so different that
it is confusing to have them both included under "gum" printing, and
that those who use pva should choose a different name for their medium.
Sil Horwitz confirmed that suspicion (that the substances are different)
>
At 2000/01/18 12:39 PM +0000, Katharine Thayer wrote:
>Is the chemical composition of pva so close to that of gum arabic that
>they can be thought of as interchangeable? I would be really surprised,
>but am ready to be enlightened by a chemist.
They are completely dissimilar. Gum arabic is a complex organic
compound,
while pva is a simple "polyvinyl alcohol." As it is proprietary, and I
don't know the constituents, I will still hazard a guess that "Gloy"
contains other ingredients than pva. I have tried pure pva and it does
not
in any way substitute for gum.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@earthlink.net
Visit http://www.psa-photo.org/
Personal page: http://home.earthlink.net/~silh/
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