Beer-Tapping Physics: Why Hitting A Bottle Makes A Foam Volcano

on 01/12/13 at 9:09 am

Beer

article-2513170-19A3145B00000578-324_634x961Ah, the old beer-tapping prank: One strong hit on the top of an open beer bottle, and poof! Your IPA explodes into a brewski volcano.

“In one second, most of your beer has really turned into foam,” says physicist of Carlos III University in Madrid. “You better have put the bottle into your mouth, because you need to drink whatever is coming out.”

Physicists know quite a bit about beer foam, Rodriguez says. They’ve pinpointed the components of barley and wheat that make a fluffy, thick head. And they’ve explained why the bubbles in Guinness instead of rise.

But the tapping phenomenon has been a long-standing puzzle in beer science — until now.

Rodriguez and his team have figured out that a stiff hit on the bottle’s top sets off miniature explosions inside the beer. These tiny blasts create mushroom clouds similar to those generated in the air by an atomic bomb.

“Actually, the laws of physics that control the development of these beer mushroom clouds are the same as [those that drive] the development of the cloud in an atomic bomb,” Rodriguez tells The Salt. “Obviously, there’s no nuclear stuff in the beer. So the source of the explosion is very different, but the mushroom cloud that you see is very similar.”

Rodriguez presented his Sunday at a scientific in Pittsburgh. But the idea for the project started where all good beer research does — at a pub.

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