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archival PVA



Jennifer wrote


In relation to this I have a question, is PVA archival? And, is
wheate paste more archival? I never seem to have this right and would
love to get educated on this matter. I have this horrible feeling
that the books I have used PVA on will go "bad".

Here is as much as I know about PVA's:
PVA, or Poly Vinyl Acetate, is a synthetic adhesive.  An adhesives
must be viscous (viscosity=resistance to flow) in order to work,
including self adhesive tape (they WILL creep).

The viscosity in PVA is controlled in two ways: The emulsion either
contains one polymer (homopolymer) to which varying amounts of
plasticizer have been added to yield glues of varying viscosities
(this is important in machine binding).  These PVA's, which is
actually the majority of PVA's on the market, will not be considered
archival, because as the glue ages, the plasticizers migrate out, the
adhesive film loses its flexibility and turns brittle.

The other option to control viscosity of the PVA is to mix two
polymers of different chain length (copolymer solution), which will
be considered archival.  As with many products, it is difficult to
find out what REALLY goes into these recipies, but we know where
there is water, high humidity and something that a fungus can feed
on, it will begin to grow.  So if your PVA has been contaminated,
chances are you might get mold growth, unless the PVA contains a
fugicide, which I would like to know about if it were PVA I am
using.

The two PVA's which I am aware of that pass as archival are Jade 403
and there was some kind of Elvace #### - I forget which is the
current number - Abbey Newsletter discussed this at great length.
ALWAYS ask about plastizers and other additives when you are
concerned about aging properties pf the PVA.

Hope this helps.

Ursula



___________________________________________________

Ursula Mitra, Conservator
Preservation Department, Mezz
NYU Bobst Library
70 Washington Square South
New York, NY 10012-1091
Tel: (212)998-2562    Fax: (212) 995-4583
e-mail: mitrau@elmer4.bobst.nyu.edu


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