What brewing method involves using a piston to extract coffee?

The brewing method that involves using a piston to extract coffee is the espresso brewing method. In this process, hot water is forced through finely ground coffee under high pressure, typically around 9 bars or more. The piston mechanism is a core element of espresso machines, which creates that pressure and allows for a quick extraction, resulting in a concentrated shot of coffee with a rich flavor and a creamy layer known as crema on top. The high-pressure extraction is critical for developing the unique flavors and aromas characteristic of espresso, which is not achieved through methods like pour-over, French press, or cold brew. Each of those methods operates differently in terms of water contact time, grind size, and extraction pressure.