This depends on the species.  Some taxa have thicker calcareous shells as
discussed by Mr. Goldberg than others so the differing
expansion/contraction rates don't cause any problems.  The real thin
(shelly layer) shelled species are the ones that blow up.    Kurt
 
At 08:29 AM 1/5/98 -0500, you wrote:
>Hi gang,
>
>I have some untreated Paryphanta that seem to hold up satisfactorily.
>However, I do know how to make them explode readily: rinse them in water,
>and they will not last many days after air drying...
>
>
>
>John Wolff                      [log in to unmask]
>2640 Breezewood Dr.             (717) 569-6955
>Lancaster, PA 17601, U.S.A.
>