Channelling is water finding a preferential path through the coffee instead of passing through it evenly. It is not exclusive to espresso.
What it looks like in a pour-over
Water running down the paper rather than through the bed. The commonest form, and it happens when you pour too close to the edge.
A crater in the bed on one side, from an aggressive off-centre pour.
Grounds stranded high on the wall, dry, contributing nothing.
Very fast draw-down with a weak, sour result.
The causes
Pouring on the paper. Keep the stream in the middle two-thirds of the bed.
An uneven bed at the start. Level the dry grounds before the bloom.
Aggressive pouring eroding a hole through the bed.
A shallow bed in a large dripper — not enough depth for the water to find resistance.
The fixes
Level the grounds and tap the dripper before brewing.
Stir or swirl during the bloom so the bed settles evenly.
Pour in controlled concentric circles, never onto the wall.
Swirl at the end — the Rao spin — to bring stranded grounds down and flatten the bed.
Reading the spent bed
The most useful diagnostic. A good brew leaves a flat, even bed with a slight dip in the middle.
Grounds stuck high on one side, or a deep crater, tell you exactly where the pour went wrong.
Last reviewed 8 August 2026