Injectable foam for furniture

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

>Christian Imhoff <imhoff_c [at] hotmail__com> writes
>
>>... Very accurate
>>indications allowed us to build a transparent PMMA negative mould
>>that represents the upholstery's original shape. Putting this
>>negative mould on the conserved upholstery (= positive mould) results
>>in voids in between, which we want to fill by injecting a foam that
>>best fulfills conservational requirements.
>
>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.

I agree with Victoria in the inadvisability of using urethane foams.
Besides the thermal problems, many of them produce poisonous gases,
cyanide for instance, that cannot be filtered by respirators.  This
means using them is a high health risk, too.

I ran across an interesting mold making idea at Mayo Clinic.  For
cancer patients, they make molds by laying them in pillows of a
polymer film bag filled with tiny polymer pellets.  A vacuum is
drawn and the bag retains the shape of the person.  I plan on
playing with this for mannequin construction, but it would work for
other large-scale mold taking applications, too.  No heat, no mess.
And it can be reused, just release the vacuum. These molds hold up
for months in their shape--while patients undergo daily radiation
treatment.

Helen Alten


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                  Conservation DistList Instance 23:43
                   Distributed: Tuesday, May 4, 2010
                       Message Id: cdl-23-43-001
                                  ***