Tamping

Tamping is the step where you press the loose coffee grounds inside the portafilter basket into a flat, firm, and level puck before locking it into the machine. The goal is an even surface with no gaps or slopes, so pressurized water meets consistent resistance across the whole puck instead of finding an easy path through one side.

The exact pressure used matters far less than levelness and consistency; many baristas simply tamp firmly and repeatably rather than aiming for a specific number of pounds of force. A tilted tamp, uneven distribution before tamping, or tapping the portafilter afterward can all crack the coffee bed and create weak spots that water rushes through.

A tamper should match your portafilter's basket diameter closely, since a loose fit leaves an uneven rim of loose grounds around the edge. Distribution tools and tamping mats help keep the process consistent between shots. A common mistake is tamping before properly distributing the grounds, which locks unevenness into the puck before pressure is even applied.