Science in the Public Interest: The Beer Koozie Test

How well do beer koozies actually work at keeping your beverage cold?

Putting beer koozies to the test.
Putting beer koozies to the test. Lisa Bramen

With the official kick-off of outdoor barbecue season this weekend also comes an alarming increase in beer waste. According to the Bureau of Bogus Statistics I Totally Just Made Up, as much as a third of every beer opened during the summer months goes unconsumed. The primary reason: the beer has gotten warm. When the mercury climbs, canned and bottled beverages don’t stand a chance of remaining palatably cold to the finish. With sodas or mixed drinks, it’s no big deal—just add ice. But beer doesn’t taste good with ice (even, in my opinion, when “ice” is just in the name).

Some people might say, “I don’t have that problem. I drink my beer in one long guzzle so it never has a chance to get warm.” Those people might have problems beyond warm beer.

For the rest of us, some marketing genius out there invented the koozie. The koozie, in case you are unfamiliar with the term, is a little foam insulating sleeve that fits around an aluminum can or, in more recent versions, a bottle. No one seems to know the origin of the name (or of the product itself, which became popular sometime in the 1980s), but my best guess is that it is a corruption of the word “cozy”—as in a tea cozy, meant to keep the teapot warm—with an extra “o” so it sounds like “cool.” Switching the “c” to a “k” must have been a byproduct of the era when bastardized spellings and superfluous umlauts were considered cool (see “Mötley Crüe”).

Whatever the origin, the koozie has several undeniable benefits: It keeps your hand from getting cold and covered in condensation. It’s a good way to identify one’s beer at a party, where it could easily be confused with look-alikes—the second most common cause of beer waste, according to the BBSITJMU. It can be used as camouflage: a friend of mine who was pregnant, but not ready to reveal her status to friends, covered her nonalcoholic beer in a koozie to avoid arousing suspicion. Finally, it’s a personal billboard, allowing you to proclaim your allegiance to a sports team; declare important sentiments, like that you’re “not as think as you drunk I am”; or go formal with a tuxedo koozie. You can even support independent crafters by buying felted, crocheted or cowhide koozies on

But how well do they actually work at keeping your beverage cold? In the interest of preventing beer waste, I put them to the test. Recently, my husband and I conducted an experiment with three bottles of beer: I held one in a koozie, my husband held one without, and a third one, also koozieless, was set down between sips. We drank them at the same rate, alternating between the two held beers and the third beer, stopping at five-minute intervals to evaluate the temperature. The air temperature was 67 degrees Fahrenheit (not exactly sweltering, but it was early evening).

Within five minutes, there was already a subtle but noticeable difference between the beers we were holding—with koozie and without—and the unhandled one. The latter was still frosty, while the others had already started to lose their chill. The gap widened over the next ten minutes. At 15 minutes, the one without the koozie was warmer than the one with, but the unhandled beer was still coldest. Finally, at the 20-minute mark, all three were less than refreshing, but the one that had been held least remained coolest.

Our conclusion: the koozie helped, but not as much as limiting the beer’s time in hand.

Would the results have been different if we were using cans? If the air temperature had been warmer (especially if it had been warmer than human body temperature)? If we had a beer in a koozie that we set down between sips?

Hard to say. If any science-minded beer drinkers out there care to conduct their own experiments, be sure to let us know the results.

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