Beer stone is a hard, grayish-brown crust that builds up inside draft lines, faucets, couplers, and shanks. It's made of calcium oxalate. Calcium and oxalate are both in beer. Over time they come out of the beer and stick to whatever they touch.
Why Your Regular Cleaning Leaves It Behind
The routine cleaning every two weeks uses caustic cleaner. Caustic breaks down organic buildup like proteins, yeast, and biofilm. Beer stone is a mineral. Caustic has no effect on it.
So a bar can clean every 14 days, right on schedule, and still build up beer stone the whole time. The caustic strips off the slime on top. The mineral layer underneath stays and grows.
Why It's a Problem
New tubing is smooth inside. Beer stone makes it rough and full of tiny pits. The Brewers Association Draught Beer Quality Manual points out that beer stone gives bacteria a place to hide. Cleaner has a harder time reaching them there.
That shows up two ways:
- Off-flavors that keep coming back. The lines get cleaned, the beer tastes fine for a few days, then the sour or stale taste returns.
- Foam. CO₂ comes out of the beer at rough spots. A crusty line or faucet pours more foam. See why draft beer gets foamy.
How to Remove It
Beer stone dissolves in acid. Line cleaning acids are usually phosphoric acid based. The Brewers Association recommends an acid cleaning every quarter.
Order counts. Caustic goes first to strip the organic layer. Then acid goes through to dissolve the mineral that was under it. Then the lines get a full rinse. Most quarterly visits do both in one trip. Our post on alkaline vs. acid line cleaning covers the two chemicals side by side.
When It's Too Far Gone
A line that has gone years without acid may have too much crust to clear. If off-flavors stick around after acid cleanings, or you see flakes coming out of the line, it's time to replace it. See when to replace draft beer lines.
Never Had an Acid Cleaning?
If your system has only ever had caustic, you have beer stone. The only question is how much. Schedule an acid cleaning and add it to the calendar every three months after that.
We do quarterly acid cleanings as part of our regular service. Call (267) 282-1002.