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Subject: Polyester resin objects

Polyester resin objects

From: Marilyn Fox <>
Date: Saturday, September 30, 2006
Detlef Klein <detlef.klein [at] inspire__net__nz> writes

>Meghan Mackey <mtmackey [at] tds__net> writes
>>I am looking for input from anyone with experience working with cast
>>polyester resin objects, especially tacky (as in sticky) polyester
>>An installation of over 200 cast polyester resin books made between
>>1975 and 2003 is being cleaned and readied for installation. Many of
>>the books have tacky surfaces.  This has caused dust and grime to
>>adhere to the books.  ...
>Reading your description of some of the objects having tacky
>surfaces, I wonder whether this is because the polyester is breaking
>down ...

I wonder if the objects are actually polyurethane resin rather than
polyester resin.  Weeping and stickiness are quite common in older
polyurethane objects as the older ingredients were less stable.
Older polyurethanes do weep an oily substance.  I don't know of any
way to stop this degradation, although I suppose the substance can
be washed off if that won't damage the object.

I can't think of cases of polyester resin, once fully cured,
becoming tacky.  It takes very little of the catalyst for polyester
resin, methyl ethyl ketone peroxide, to cause the polyester resin to
harden. The mixture would have to be radically uneven to preclude an
eventual cure, so that the object would probably still be very
sticky when pulled from the mold.

I haven't had much luck with using acrylic adhesives with resins,
they often fail to stay adhered, probably due to residual oils in
the resin.  I've usually found that regluing with the original resin
holds better, if that's possible.

Marilyn Fox ( [at] yale__edu)
Preparator, Division of Vertebrate Paleontology
Peabody Museum of Natural History
Yale University
170 Whitney Avenue
New Haven CT USA 06511
PO Box 208118
New Haven CT USA 06520-8118

                  Conservation DistList Instance 20:19
                  Distributed: Monday, October 9, 2006
                       Message Id: cdl-20-19-002
Received on Saturday, 30 September, 2006

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