Popcorning is beans jumping around above the burrs rather than being drawn in, at the end of a dose.
Why it happens
Burrs feed by pulling beans down. That relies on weight from the beans above pushing them into the gap.
With a full hopper there is plenty. With a small single dose, the last few beans have nothing above them and bounce off the spinning burrs.
Why it matters
It takes longer, sometimes several extra seconds of noise.
The last beans are ground differently — bounced and struck rather than fed steadily — which slightly widens the distribution.
Beans can escape back up the throat.
The fixes
A weighted bean tube. A small metal cylinder that sits on top of the beans and supplies the missing weight. The standard solution, and effective.
Some grinders ship with one; aftermarket ones exist for most.
A narrower throat. Grinders designed for single dosing have a restricted throat so a small dose still sits in a column.
A bean funnel rather than a full hopper, which also keeps beans out of the light and air.
Which grinders suffer
Those with wide throats designed for hoppers, used for single dosing. Converting a hopper grinder to single dosing usually needs a bean tube.
Grinders designed for single dosing from the start rarely popcorn.
How much does it matter
Modestly. It is a small effect on distribution and an audible annoyance. Worth a cheap bean tube, not worth a new grinder.
Last reviewed 8 August 2026