Polyurethane foams degrade, and as Jordan implies, and should not be used.
polyethylene and polyester foams are safe.  They are not as compressable
as polyurethanes.  Some are fairly rigid but can be cut so a shell can be
placed in them.

Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History, Pittsburgh, PA
Assistant Professor - Family Medicine

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On Thu, 6 Jan 2000, Jordan Star wrote:

> Do not use foam of any kind.  It disintegrates and makes a sticky goo on the
> shell.
> Jordan *
>