The University of Illinois provides visitors to its website with various science fair projects, including the perennial favourite – “Can air pressure alone cause an egg to be pushed into a bottle?”. Of course, it can. To make it work you’ll need an egg, a bottle, and a couple of matches. It’s all to do with air pressure differences.
But, the procedure Illinois suggests students to follow begins with “Step 1 – Peel the shells off the eggs”.
Not until further down the page (below the fold in fact) does it mention a crucial preparatory step. Can you guess what it is? Or, would you end up with egg on your face, and all over your hands?
You can watch a video of this kind of egg in a bottle experiment here.