Frosty beer mugs are a staple in many bars, but you don't need them for every beer. Serving beer too cold can hide the flavor. The optimum temperature for serving most craft beers is 40 to 55 degrees Fahrenheit, so refrigerated bottles don't require further chilling. Save the frosted mugs for when you are pouring from an unrefrigerated bottle.
The Right Glassware
Although you can frost any type of mug, thicker mugs work best. It may take a thicker mug longer to get cold and frosty, but the thicker glass walls will also warm up more slowly so your beer will stay cold longer. When chilling any glass, make sure that it is at room temperature. Applying freezing temperatures to a hot glass can cause it to crack or shatter.
Keeping the beer mugs in the freezer ensures that you always have a frosty glass ready for your next pour. It can take up to 10 minutes for the temperature of the glass to drop below 32 F, depending on your freezer temperature. Make sure that the inside of the glass is dry when you place it in the freezer, otherwise the moisture will freeze and then dilute your beer as it melts.
Quick Chilling with Ice
If you don't have a freezer handy or if you need to speed up the frosting process a bit, you can use ice to frost your mugs. Simply fill the mug to the top with ice, and then top it off with cold water. Wait about six minutes for the glass to chill and become frosty, and then empty out the ice and add your beer. The main drawback to this method is that moisture may freeze on the inside of the glass before you can wipe it out and pour, which can result in dilution.
Speed It Up
There are a few ways that you can chill a beer mug even more quickly. Some professional bartenders frost mugs instantaneously with liquid nitrogen, but that isn't a recommended method for the home connoisseur. A more realistic method is to wrap a wet paper towel around your mug before placing it in the freezer. This can frost the mug in as little as three minutes. If you need to frost your mug even more quickly, store vodka in the freezer overnight. Fill the mug with vodka, and then empty it out after 30 seconds to 1 minute to have an almost instantly frosted glass.