How Beer Sleeves Keep Your Drink Cooler, According To Science
If you've enjoyed beer outside, especially if it's one of the best summer beers in warm weather, there's a good chance you've used a beer koozie. Most beer today comes in aluminum, whether it's 12-ounce cans for macro beers orvtaller cans many craft breweries use, and foam and cloth koozies fit perfectly over those cans in order to control their temperatures. As beer warms, which it will outside or in your hand, the oxidation process speeds up, yielding off-flavors like wet cardboard and wax. The beer also loses its carbonation. People have been inventing different solutions to prevent beverages' temperature changes for decades — think tea cozies. However, it was Bonnie McGough's 1981 patent for the "Koozie" that came to the rescue of beer cans, in particular. But how, exactly?
Optimal beer-drinking requires a Goldilocks-like balance of not warm, not freezing. The best temperature range for light beers like lagers is around 38 to 45 degrees Fahrenheit, wheat beers work wonders between 40 and 45, and stouts and IPAs really sing between 45 and 55 degrees. When beer is too cold, aroma compounds are less active so flavors are muted, but warm beer is unpleasant, flat, and off-flavored. Koozies, therefore, do the important work of insulating beer from outside temperatures and your hand with their foam barrier. Second, they prevent condensation drops from forming, which actually heat up the can in a process called latent heat.
How koozies' insulation and latent heat prevention work
Both scientific processes happening with the humble beer koozie, insulation and preventing the effects of latent heat, delay temperature change rather than doing any cooling. Theoretically, that would also keep beer from getting too cold, which is when you'll start losing all those nice flavors and aromas. But because we more commonly employ them when imbibing in warm weather, we'll focus on the cooling end of koozies' overall temperature-steadying ability. Heat transfer from your hand or the air or any surface won't happen because of the layer of foam. The foam's little pockets trap air, keeping it from reaching the can and its beer.
Then, the reason a koozie is an important block for water droplets is because those drops are forming from water condensation in the air, a process that causes heat as a byproduct. When water melts from solid ice to liquid, for example, its molecular bonds break. At high enough temperatures, they'll keep breaking until the water evaporates into gas, which uses energy referred to as latent heat. If that vapor turns back into liquid, the way it does when it meets a cold can in warm air, the heat it required gets released — onto your can, heating the beer. That's why the koozie's simple barrier against condensation is as important as its insulating property. The simplest way to make even a cheap beer taste amazing? Maintaining the proper temperature, and the koozie's got you covered.