Foam is a symptom, not a diagnosis. Temperature, pressure, gas and equipment all play a part — here is how they connect.

A glass that is half head is frustrating for the bartender, disappointing for the customer and expensive for the owner. Foam problems almost always come back to a handful of causes — and they are connected, so fixing one in isolation often moves the problem somewhere else.

Temperature

Carbon dioxide stays in solution more readily in cold beer. Beer that warms anywhere between the keg and the faucet — a cooler running warm, a tower without proper cooling, a trunk line losing its chill — releases gas and pours foamy. The Brewers Association recommends storing and serving most draft beer at 38°F.

Pressure and gas composition

Every keg has a carbonation level set by the brewer. The applied gas pressure has to hold that level at the system’s temperature; too much over-carbonates the beer over time, too little lets carbonation escape. Long-draw systems often need a carbon dioxide and nitrogen blend so the beer can be pushed farther without over-carbonating it.

System balance

Line length, line diameter and elevation all create resistance. A balanced system matches that resistance to the applied pressure so beer arrives at the faucet at a steady, controlled flow. Changes to a system — new faucets, a moved cooler, a longer run — can upset that balance.

Equipment condition

  • Worn or dirty faucets and couplers that disturb the flow
  • Kinked, damaged or dirty beverage tubing
  • Leaking gas fittings or failing regulators
  • Glycol or cooling components that are not keeping up

Start with the whole system

Because these causes interact, the fastest path to a good pour is a complete system evaluation: temperature, pressure, gas, tubing and equipment, checked together.