Injectable foam for furniture

Victoria Gill <victoria.gill [at] endangeredheritage__com> writes

>To my knowledge injectable foams are polyurethane. The expansion of
>the foam is exothermic and can generate a lot of heat which is
>undesirable in proximity to objects. Several article have been
>written on its use and failure in conjunction with Archeological
>digs. However you are proposing pre-moulding and then using the form
>in conjunction with the object. Polyurethane off gasses and becomes
>acidic over time. Additionally in conjunction with high humidity it
>can go through cycles of weeping and wetting, as it shrinks and
>deforms.  This is detrimental to the item.

Regarding foam for use in conservation, I keep reading about
problems with heat. We have used a two part foam mixture for many
years in extremely delicate packing. We were also concerned about
heat generation. It is true that these foams generate exothermic
reaction, so we decided to measure it before considering it for use.

What led us to this was a fragile plaster over wire Giacometti
maquette where the wire was rusting, expanding and crumbling the
plaster. We had to transport it from Oklahoma to our lab in New
York. The problem at hand was being able to exert pressure on the
piece to prevent loss during the rigors of transport. We decided
that the two part foam would work if the exothermic reaction was not
extreme. To test it we purchased thermometer heads on cables from
General Electronics, and, using a mockup, we measured the exothermic
temperatures (a) at the interface between a protective surface
surrounding the object, where we anticipated the protective surface
would bleed off some of the temperature,(b) the interior of the foam
with nothing to bleed off temperature and (c) the surface
temperature (with a laser thermometer).

We repeated the experiment three times with consistent results. The
temperature at the interface was 90 degrees(F); the internal
exothermic heat was 125 degrees (F), and the surface temperature at
the interface between the ambient temperature 86 degrees (F) was 91
degrees (F). We also decided to bind the piece first in linen and
then surround it with bubble wrap to provide some insulation. We
further decide that, in that configuration, and considering the
materials of the macquette,

Based on this, we used the foam for that transport, and it rode in a
first class seat beside me to New York. Since, we have found foam to
be a terrific transport material if used judiciously.

There apparently is a maximum amount of thickness which can be
poured. The fire in the Royal Saskatchewan Museum was traced to a
foam exothermic reaction when it was poured too thickly. That being
said, I have seen pours of a foot or more without extreme exothermic
reaction. In the fire situation, I question whether the constituent
materials were correctly formulated.


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                  Conservation DistList Instance 23:44
                    Distributed: Sunday, May 9, 2010
                       Message Id: cdl-23-44-001
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