From the HBD Archive
From: willa@hpvclwa
Subject: All Shook Up
Date: 1989-10-26 22:17:43 GMT

RobertN. (robertn%fm1@sc.intel.com) writes:
>
>When the bottles are shaken, are there any affects? Pressure buildup may
>burst the bottles, but does anything else happen?

I read an article by a physics (fizziks?) professor and beer-o-phile in
Discover (Discovery?) magazine regarding shaking cans of beer. He states
that shaking does NOT increase the pressure inside the can. Remember:
PV=nRT. Shaking does not change the volume, amount of gas, temprature, or
proportionality constant. He has measured the pressure of cans, shaken and
unshaken, and it does not change. So, shaking will not cause rupture (do
not confuse with rapture ;-).

The bubbles that arise (pun intended) when the cap is popped off need places
to form. Raindrops and snowflakes also required seeds to form around. For
bubbles, a "seed" is often a point of lower pressure in the liquid. When the
beer is moving around, little vortices develop. The centrifugal force of the
spinning liquid lowers the pressure in the center of the vortices. Shaking
a can makes a lot of vortices. If you open it right away, whoooosh! If you
wait a few minutes, the vortices die down, and the beer will stay in the can.

Another interesting note: the small cloud that appears in the neck of bottles
just after popping the cap is condensation. The sudden drop in pressure can
lower the temprature of the gas in the neck to -50 F!

. .Will
..!hplabs!hpvcfs1!willa or willa@hpvcfs1.hp.com

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