Science of cocktail shaker vacuum

Ever notice that cocktail shaker cans get vacuumed together when you shake a drink? The encoldening of all the stuff inside is doing it, creating enough vac that you need to apply about 13.6 pounds of force to pull a small shaker apart.


First, the air that's in your shaker starts off at room temperature. As you are shaking, this air gets cooled just like your drink does. Cooling the air causes the pressure to go down, which causes a vacuum. That isn't all that's happening, though. Ice is less dense than water. When ice melts, it actually contracts in volume. When the volume of liquid plus ice in the shaker contracts, the volume of air in the shaker increases. Since you aren't adding more air molecules, increasing the volume decreases pressure, causing more vacuum. Third, as your liquor gets colder, its density increases, again shrinking in volume and creating more vacuum. A third factor may be a small amount of expelled air when the bartender slams down on the cans before the shake.

More Cocktail Science: Why Do My Shaker Cans Get Sucked Together?

(via JWZ)

(Image: Cocktail Shakers, a Creative Commons Attribution (2.0) image from walkn's photostream)

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