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Re: The PVA collection

On Tuesday, November 30, 1999 11:10 PM, Artemis BonaDea
[SMTP:paradux@alaska.net] wrote:
> Years ago I was told that bookbinder's PVA and Elmer's glue had a very
> similar forumla but were manufactured using a different process.  I'm
sorry I
> can't remember the source.
> I was told that adhesives are manufactured with several components:  in
> case a liquid componendt that allows the glue to flow and an adhesive
> component that allows the glue to stick.  There are also dryers and such
> it's amazingly complex to create adhesives.
> My source told me that in Elmer's glue, the two layers (carrier and
> lay on top of one another.  While in binder's PVA, the two layers are
> together so the adhesive and carrier are intermingled and that is why the
> is more flexible where the Elemer's glue is more rigid.
All PVA glues are fundamentally the same thing: An emulsion of Poly(vinyl
acetate) droplets suspended in a water-based carrier. What differs among
them is the molecular weight (degree of polymerization), purity (or, more
specifically, the lack of impurities--particularly acetic acid left over
from the polymerization), and additives that affect the flexibility of the
dried glue film.

Although the carrier liquid might be neutral or alkaline, the dried glue
can nevertheless give off acidic compounds, and can therefore become acidic
as the glue ages.

I dug around in our old files, and finally found a report (dated 1992) from
the Canadian Conservation Institute, entitled in part "An Evaluation of
Selected Poly(vinyl acetate) and Acrylic Adhesives", which tested glues
over 5 years of aging (in light and in the dark) for glue film pH, emission
of acetic acid vapour by the glue, flexibility, and yellowing. None of the
tested glues fared well in all categories. In particular, most of the PVA
glues started off acidic, and those that did not became acidic with aging
in light.

I am not sure if it is still possible to get copies of this report. Just in
case, the full reference is:
Adhesive Testing at the Canadian Conservation Institute - An Evaluation of
Selected Poly(vinyl acetate) and Acrylic Adhesives
by Jane L. Down, Maureen A. MacDonald, Jean Tetreault and R. Scott Williams
CCI Environment and Deterioration Report number 1603
Written 1992, Third printing January 1994
Published by the Canadian Conservation Institute, then a branch of
Communications Canada.
This institute is now under the Heritage ministry; their web site is
I can't find this publication at that site, although I did find a couple of
other interesting publications...

Kevin Martin
the Papertrail

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