Awhile back someone posted a thread about how you could submerge an egg in vinegar overnight and the vinegar would dissolve the eggshell, leaving the membrane and inside of the egg intact. I was really REALLY bored last night, so I tried it. We only have apple cider vinegar and the egg still looked normal this morning, so I thought I'd give it more time. I just drained off the vinegar and it worked! The result looks and feels really weird and it bounces when you poke it.