How Does an Espresso Machine Work?

A pump-driven espresso machine heats water to 90–96°C and forces it through a compressed puck of finely ground coffee at 9 bars of pressure (roughly 9 times atmospheric pressure). The water passes through about 7–9 grams of coffee in 25–30 seconds, extracting oils, sugars, and aromatic compounds that create the rich flavour and characteristic crema — the golden foam on top. The crema forms because CO₂ trapped in freshly roasted beans is released under pressure and emulsified with coffee oils. Commercial machines use rotary pumps for consistent pressure, while home machines typically use vibratory pumps.