Re-carbonating my beer with a sharp rap

Dear Matthew Alice: In my college days, it was "common knowledge" that a sharp rap on a cold beer would “reinfuse” the carbonation and prevent or reduce the foam and spray when the can was opened. Is there any truth to the physics of this? The question really revolves around the state of a pressurized liquid at a given temperature when it is agitated and ready to bubble into foam. Will the rap somehow return that can toward the condition of a similar but unagitated can? To shake the can adds energy. How would the additional energy of the rap help? Is there a simple science fair project in here? — Dennis Coates, Solana Beach

Dang, man. Too much thinkin’ going on behind this little question. So here’s another public service announcement in my continuing campaign to wipe out “common knowledge,” scientifically proven to be the cause of 40 percent of today’s mayhem and gum disease.

Nothing you can do will moosh carbonation back into a brew. Bubbly beverages are very unstable, and carbonation wants only one thing — freedom. Any jostle, tap, thump, rattle, tip, spill, or shake gives it the excuse it needs. Unopened, the can contains enough pressure to keep the carbon dioxide trapped in suspension. But pop the top and you liberate all that agitated gas. That rap with the class ring soothed only the rapper, not the rappee. So much for common knowledge, collegiate or otherwise.