Milk foams when air is introduced into it and then broken into small bubbles by a vortex. If foam is not forming, one of those two phases is failing.
The wand tip is too deep. If you hear a low rumble and see the milk spinning but not rising, no air is going in. The tip needs to sit just below the surface at the start — you are listening for a light, steady tss-tss.
The milk is already too hot. Milk stops taking in air somewhere around 37 °C (99 °F). If you spent ten seconds getting the wand positioned before starting, the window has closed. Position first, then turn the steam on.
The pitcher is too full. Milk roughly doubles in volume and it needs room to move. Fill between one third and one half.
Your steam is weak or wet. Single-boiler machines need a moment to reach steam temperature, and the wand must be purged first — the water sitting in it will otherwise dilute the milk and kill the foam.
If it foams and then collapses
That is a different fault: you stretched but did not spin. Adding air makes big unstable bubbles; the second phase, with the wand deeper and off-center, breaks them down and folds them through. Skip it and the foam sits on liquid milk and separates within seconds.
Keep spinning until the surface looks like wet paint — glossy, no visible bubbles, moving as one.
If it is the milk
Skim milk foams easily and coarsely. Whole milk foams a little less easily and considerably better, because fat stabilizes the bubbles. Long-life milk foams unpredictably. And most standard plant milks foam poorly — you need a barista edition.
What people want to know
How full should the pitcher be?
Between a third and a half. A 500 ml pitcher is right for 150 to 250 ml of milk. Under-filling is as bad as over-filling — the vortex needs volume to form.
Does the pitcher need to be cold?
Cold milk gives you a longer working window before it passes the temperature where air stops incorporating. A chilled pitcher helps for the same reason.
Last reviewed 30 October 2026