You might be asking yourself, what is a glass rinser and why would I need one? I’m sure you’ve seen them in bars and restaurants before. They are normally on the counter and shoot up jets of water into the glass to clean it out. They are gentle enough for wine glasses and strong enough to get any remaining dish soap washed away.
Glass rinsers aren’t there to sanitize steins, they only shoot up jets of water so you should still wash your glasses after every use. The most useful aspect is what every wine or beer drinking savant knows, they clean the glass. It washes away any dust, detergent, or leftover wine (perfect for if you plan on having glasses of different wines yet don’t want to completely sanitize glasses).
Rinsing a glass before filling it with beer will also help minimize friction. This will in turn help your chances of a smooth, even pour. Beer aficionados know that the right amount of foam (or head) is preferred to open up the aromas of the beer and focus the flavor profiles. Less friction will also help in this endeavor.
A cold rinse will lower the temperature of your glass. Have you ever chilled a glass in the freezer before pouring a beer in it? The drink stays cool for a little while longer. It’s the same concept with cold water rinsing the glass.