Channelling

Water finding a path of least resistance through the puck, bypassing most of the coffee and extracting intensely from a narrow zone.

Category: Extraction — Workflow & Technique

When water finds a path of least resistance through the puck — typically a single channel or fissure where water rushes through faster than the rest. Produces uneven extraction and visible spritzing on a bottomless portafilter.

Why it matters — Channelling is the single biggest cause of inconsistent shots. The water in the channel over-extracts; the rest of the puck under-extracts. The cup tastes both bitter and sour at the same time.

Good to know

Fix the puck prep — more WDT, better levelling, check the tamper fit, ensure the basket walls are clean.
A bottomless portafilter shows channelling immediately. If you see side-spray or one fast stream from the centre, the puck has a channel.