I’ve removed plates from my dishwasher only to find that there’s still a small plop of sauce cemented to the rim. It happens at restaurants and bars, too, only sometimes when the staff is busy and the lighting is low, a server or bartender can miss it. Then you, poor customer, end up with a dirty glass.
But there’s a super-simple trick to find out whether your glass is dirty, and all it takes is one second: Once your draft beer is served to you, check whether the carbonated bubbles stick to the sides of the glass. If they do, they’re catching onto soap residue or leftover crud on the walls of the glass. It’s that simple. This happens most often with stackable glassware like pint glasses, which carry dust on their bottom and deposit it inside the glass they’re stacked into. Bartenders should be extra careful to rinse or wipe these glasses before serving beer in them.
Dirty glasses are a point of contention in the beer world, where “beer-clean” glassware has been a rallying cry for years. In a clean glass, bubbles don’t cling to the sides; they travel straight up to join their brothers and sisters in the head of your beer. So if your glass looks like any of the ones above, politely ask your bartender to pour you another—unless of course you want to know what flavor lip gloss the gal before you was rocking.