Video explanation
The espresso machine builds pressure, pours, drips and replaces the cup. Pump pressure, cup volume and boiler pressure change throughout the cycle.
Pressure from the pump
A pump pushes hot water through a resistive coffee puck. Pressure works together with flow rather than independently making coffee stronger.
Heat and extraction
Hot water dissolves soluble coffee compounds. Temperature, grind, dose and time matter alongside pressure.
Brewing and steam
The display distinguishes brewing and boiler states. Brewing water and steam serve different tasks, and pressure falls as the cycle ends.