At lunch today with my CPT, and two of our translators, (one who is like 24 and the other who's like 50ish) the server handed us all canned sodas. I take mine, and like subconciously, like normal, I tap the top of the can to make sure it doesn't explode when I open the can. Our younger interp looks over at me and says, "Why do Americans tap the top of the can before they open it, because I've started doing it and I've been saying to my self 'you IDIOT, you keep tapping the top of your can and you have NO idea why you're doing it!' so please tell me why you do that?!?" I'm just rolling on the floor at this point, so, I stop laughing long enough to explain it knocks the bubbles off the sides of the can, keeping it from exploding when you open it. He looked SO relieved when I finished. So, now he knows why he's tapping the top of the can. LOL.