One of the Silliest Things You Can Do With an Egg
one raw white hen's egg
Place the egg in a jar. Cover with vinegar. The second day, change the vinegar. Put the egg away. Don't look at it for about a week (sometimes it takes longer). Just let it soak away in the vinegar. After a week, the egg should be translucent but still pretty much egg-shaped. The vinegar eats away the shell (which is mostly calcium), leaving the membrane intact. Some of the vinegar permeates the membrane, and since this vinegar takes up more space, the membrane will stretch to accommodate it. This is why the egg looks a little bigger. If you shake the egg, you can see the yolk sloshing around in the white. If the membrane tears, the contents will spill out just the same as with any raw egg, only now they have been "pickled" in the vinegar.
If you do this with a hard boiled egg, the shell will dissolve in the same way, and you will be left with a rubbery egg that should actually bounce (if not dropped from too great a height).
If you are in a very silly mood, try soaking a bone in vinegar for several days to a week. If the bone was fresh enough, you should be able to bend it; even tie a knot in it. This is because most of the calcium has been dissolved, leaving behind other less rigid parts of the bone.