Espresso without the mystery
Dose, yield and time: the three numbers behind every shot, plus steaming milk.
Espresso looks like magic: a small, thick, intense drink with a golden crema on top. In fact it follows the same rules as any other coffee. Water extracts flavour from ground coffee; espresso just does it very quickly, under pressure. Once you understand three numbers, dose, yield and time, espresso stops being a mystery.
What makes espresso different
An espresso machine pushes hot water through a tightly packed puck of finely ground coffee at about 9 bar of pressure, nine times the pressure of the air around us. The pressure lets the water extract a lot of flavour in about 30 seconds. It also emulsifies coffee oils into the drink, which gives espresso its thick texture and crema.
Because everything happens so fast, small changes have large effects. A tiny change in grind can change the taste completely. That is why espresso needs more care than pour-over, not more magic.