Bruce Weertman writes:
1. a duck egg works better but a regular old egg will work too.
2. poke small holes in the egg at opposite North/South holes
3. blow all the egg stuff out
4. soak the egg in vinegar for ~10 days The shell dissolves off and you're now left with an empty rubbery shell of an egg.
5. remove from vinegar, dry and powder with talc. Store with talc on it.
OK now for the magic trick...
1. hold the hollow egg in your hand showing the audience.
2. squeeze your hand shut and the egg will appear to vanish.
3. do a slight of hand
4. The egg can be made to reappear by drooping the crushed egg into a cup and shaking.
I saw a magician do a long trick with this and was quite amazed!"