Pre-infusion

Pre-infusion is a brief, gentle wetting of the puck at low pressure before the machine ramps up to full brewing pressure (typically around 9 bar). Instead of hitting dry grounds with the full force right away, water soaks in slowly for a few seconds, letting the bed swell and equalize.

Why it matters: dry, compressed grounds resist water unevenly. Blasted with full pressure straightaway, water carves low-resistance paths through weak spots, a defect called channeling that causes uneven, often bitter and sour extraction. A soft start lets the puck absorb water gently, close up cracks, and present a uniform face to the high-pressure phase that follows. The payoff is steadier flow and more even extraction.

You will see pre-infusion delivered different ways: a spring-loaded lever machine does it naturally, a pump machine may hold at line pressure for a few seconds, and machines with flow or pressure profiling let you shape it precisely. Even a short pause helps. It pairs well with careful puck prep for forgiving, repeatable shots.