Another adhesive that will probably work is Butvar-76.  It is a glue used
in paleontology.  It comes as a powder that is mixed with acetone.  A
thick solution makes an adhesive, a thinner solution makes a consolidant.
The advantage of using Butvar-76 is that whatever you do can be undone.
All that one has to do is resoak a specimen in acetone, the Butvar softens
and you can remove the shell.  I purchased 2 lbs. of Butvar from the
Florida Paleontological Soc. about 6 years ago and I'm still not finished
with the first pound.  A little goes a long way.  I have also heard that
some hobby or model cements are Butvar based but I do not know if anything
else is added to them that would affect their property of being
reversible.
There are other versions of Butvar other than the Butvar-76 form, I am not
familiar with them, there are also other organic polymers that are soluble
in alcohols or water.  There may be easier to use than a Butvar-76/acetone
mixture but I have no experience using them.
 
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History
Assistant Professor - Family Medicine
 
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