As dramatic as it sounds, bands of bubbles that cling to the sides of a freshly poured beer indicate the place you ordered it from has no business in serving beer.
Here I am, at a restaurant in a packed food hall, looking at my locally made lager as if it’s an anti-vaxxer’s kid with measles. Do I drink it out of shame, or send it back as though it were a food-crusted dirty fork?
Bubbles clinging to the side of a glass indicate one thing: The glass is dirty. Scientifically speaking, bubbles form on nucleation sites inside of a glass with dirt, oil or grease deposits. And that means the beverage you just ordered is marinating in leftover dirt and grime.
Not only does dirty glassware look gross, but it can also affect the taste and perception of the beer. The extra nucleation sites allow more CO2 to escape your beer faster, meaning it will get flat quickly. Instead of that perfect foam-top head, unclean glassware will lead to a head that dissipates. As you drink, the telltale “Brussels lace” won’t follow the liquid down from sip to sip. Getting a gross glass is also a key indicator the place that served it doesn’t regularly clean its draft lines and beer faucets, which can cause a rainbow of off flavors.
Most brewery tasting rooms have an impeccable glass-cleaning regimen, so much so I’ve watched a beertender throw out a beer and repour in a new glass more than a few times. If you see unclean glassware at a restaurant, maybe it’s time to drink elsewhere.
Greg Nagel has been writing about beer since 2011, is an avid homebrewer of wine, cider, and beer, is a certified Cicerone Beer Server, level 1 WSET in Wine, a podcaster with the Four Brewers Show, and runs a yearly beer festival called Firkfest happening this June!