Technique
What Is Pre-Infusion and Why It Matters
Pre-infusion is a short, low-pressure phase before full extraction pressure, and it solves a specific, common problem: uneven water flow through an imperfectly prepared puck.
What happens during pre-infusion
Water enters the puck at low pressure first, saturating the grounds evenly before full pump pressure is applied. This gives the coffee bed a moment to swell and settle before it has to withstand the full force of extraction pressure.
Why even saturation matters
An unevenly saturated puck lets water find a path of least resistance once full pressure hits — channeling — which produces a shot that is simultaneously under-extracted in some parts and over-extracted in others (see our channeling guide). Pre-infusion reduces how much an imperfect tamp or distribution punishes the resulting shot.
What to expect without it
Machines without pre-infusion can still produce great shots, but they typically demand a more even tamp and a more consistent grind to avoid channeling, since they skip the step that forgives minor unevenness. A less experienced user is more likely to notice channeling-related sourness or bitterness on a machine without pre-infusion.
How to tell if your machine has it
Watch the first few seconds after starting a shot: a visible slow drip or gentle wetting stage before the stream picks up to full flow is pre-infusion at work. If flow jumps immediately to full force with no gentler initial stage, your machine likely does not implement it, which makes distribution and tamp technique more important to get right.