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Subject: Microballoon mixture for wood

Microballoon mixture for wood

From: Barbara Appelbaum <aandh>
Date: Thursday, March 23, 2006
Eugenia Stamatopoulou <stamatopoulou [at] deste__gr> writes

>This query is posted on behalf of Maria Filipoussi
>
>    Does anybody have information about epoxy resin/phenolic
>    microballoons mixture as a filler for wood objects? I am looking
>    for a commercial brand name and suppliers in Europe.

Some of the issues related to the use of this (and other) materials
is exactly how they are being used.  A rigid epoxy poured into a
sizeable loss in a wooden object can create problems no matter what
the aging properties of the epoxy are.  On the other hand, if a hole
is filled almost up to level with an inert material like ethafoam
and a cast is made of the opening so that a solid piece of epoxy can
be set back in with a an easily soluble adhesive, some of the
less-than-desirable properties of a sub-optimal material might not
matter so much.

On yet another hand, it seems better to use an epoxy only when more
soluble materials aren't suitable.  For large fillings, shrinkage of
materials that harden by evaporation *is* a problem, as is the
introduction of lots of water or solvent to an enclosed space, but
they both can be mitigated with additives like those suggested by
Ms. Arnold.  If the filling is needed to provide structural support,
of course, then the situation changes.  It is always helpful (when
planning treatments *or* asking questions about one) to be as
specific as possible about the purpose that a material
serves--another problem with epoxy is the ability to adjust gloss,
texture, etc. to match the surrounding surface.

I have tried B-72/microballoon mixtures.  For inexplicable reasons
that I'm sure many would agree with--and many not--I hate them.  I
find them too soft and too marshmallow-fluff-y.  However, I made up
a few batches with added PVA resin (with or without the B-72) and
found stuff that has a really nice spreadability.  I have a bunch of
jars with various colors of mixtures with resin, cellulose powder,
fumed silica, microballoons, and/or the kitchen sink.  They dry hard
in the jar, but a little acetone dripped in and left for a few
minutes turns them nice and soft.  I suppose they would be nasty and
impractical for large fills, but a lot of different
conservation-grade materials can be combined in the same ways to
make gesso-like materials.  (Ethyl cellulose and fillers, for
example.)

Barbara Appelbaum
Appelbaum and Himmelstein
444 Central Park West
New York, NY  10025
212-666-4630


                                  ***
                  Conservation DistList Instance 19:47
                 Distributed: Wednesday, March 29, 2006
                       Message Id: cdl-19-47-001
                                  ***
Received on Thursday, 23 March, 2006

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