All coffee guides · Espresso Technique
Pre-infusion is the phase before full extraction pressure is applied to the coffee puck. Instead of hitting the puck immediately with nine bars of pressure, the machine first wets the grounds at low pressure, allowing them to swell and settle before the full extraction begins. The idea is that a more uniformly saturated puck extracts more evenly and with less channeling.
When full pressure hits a dry coffee puck instantly, the water takes the path of least resistance — typically through whatever gaps or weak points exist in the distribution. This pressure spike can also blow channels through the puck before it has fully saturated and expanded. Pre-infusion aims to fill those gaps gently first, so the puck is structurally uniform before the high-pressure extraction begins.
In most consumer machines, pre-infusion works by delivering water at low pressure (around 1-3 bar) for a set number of seconds before ramping to full brewing pressure. Some machines use a mechanical pre-infusion created by a small reservoir that fills before pressure builds. More advanced machines (Decent, La Marzocca, some Breville/Sage models) allow you to control the duration and pressure of pre-infusion as part of a programmable profile.
Many modern consumer espresso machines include some form of pre-infusion, often enabled by default and not widely advertised. E61 group head machines have a built-in mechanical pre-infusion due to the way water fills the group chamber before pressure builds. Some entry-level machines skip it entirely. Check your manual. On machines like the Breville Barista Express, Sage Barista Touch or Lelit Mara, pre-infusion settings are adjustable.
For most home setups, pre-infusion provides a noticeable improvement in consistency — particularly on lighter-roasted, harder beans that are more prone to channeling. The effect is most visible on a bottomless portafilter: with pre-infusion, the puck saturates more evenly before the mushroom of espresso begins to form. The improvement is more significant with coarser grinds and light roasts than with fine grinds and dark roasts, which are less prone to channeling in the first place. If your shots channel frequently, enabling or extending pre-infusion is one of the first things worth trying.
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