Espresso shot

An espresso shot is made by forcing hot water, usually just under boiling, through a compact puck of finely ground coffee at around nine bars of pressure. The result is a small, concentrated drink, typically eighteen to twenty grams of ground coffee yielding thirty six to forty grams of liquid in around twenty five to thirty two seconds.

Because the process is so fast and concentrated, small changes matter enormously. A shot pulled too fast tastes sour and thin, one pulled too slow tastes bitter and harsh, and the difference between the two can be a second or two of time or a hair's width of grind adjustment. Crema, the reddish brown foam on top, is a visual cue but not proof of quality on its own.

Buying an espresso machine means deciding between single boiler, dual boiler, and super automatic designs, which trade off price, speed, and how much manual control you get over the shot. A common mistake is expecting espresso quality from a cheap or worn grinder, since grind consistency matters as much as the machine itself.