Freeze them!!! That is the only way I have found to store stones without them melting away. You don't want your prize stone to melt away to nothing. Its so great to get the word out about flushes- never thought of a Science fair. Too bad my son is only 3. Maybe when he's a little older. I must congratulate your bravery also. I have had to schedule flushes strictly for weekends because I am afraid to go anywhere the morning after!