I've always preserved my microshells by desicating them by soaking in
isopropyl alcohol (70%) several days, rinsing in fresh water and then
drying thoroughly.  Frankly, I used isopropyl alcohol because it's cheap,
readily available, and it never dawned on me that it wouldn't be adequate.
Recently a new friend recommended 75% ethanol (Everclear 153 proof) as
superior.  My questions to the experts on Conch-L, for the enlightenment of
us all, are:
 
1.  What's the difference?
2.  What are the merits, pitfalls and consequences of one over the other?
3.  Is there something better than either?
4.  What is the best technique to thoroughly desicate (to odorless)
somewhat larger shells (about the size of Nerita tessellata)?
 
Marlo