Channeling

Channeling occurs when water finds paths of least resistance through the coffee puck during espresso extraction, rather than flowing evenly. This creates uneven extraction - some areas are over-extracted (bitter) while others are under-extracted (sour). Visual signs include streams of dark liquid, sputtering, or an uneven flow from the portafilter. Channeling is caused by uneven tamping, inconsistent grind distribution, clumps in the coffee, or an uneven coffee bed. It's one of the most common problems in home espresso making. Solutions include using a distribution tool (WDT - Weiss Distribution Technique), ensuring level tamping, using fresh beans, and maintaining consistent grind quality. Proper puck preparation is key to preventing channeling.