What espresso actually is
- Espresso is hot water pushed through fine coffee at about 9 bar, in under half a minute.
- Start near 1:2 by weight — 18 g in, 36 g out — in about 25–30 seconds, then taste.
- Crema is foam from roasting gas. Fresh beans and robusta make more; it proves nothing.
Pressure, not patience
Espresso is hot water forced through a tight bed of finely ground coffee, held in the metal basket of a portafilter, at about 9 bar — roughly nine times the pressure of the air around you.
Minutes, or half a minute
Filter coffee, or espresso?
- Filter coffee
- Minutes, not seconds
- Gravity does the pushing
- Espresso
- Under half a minute
- A pump at about 9 bar
- Oils and tiny particles in the cup
Espresso is the pushed one: under half a minute at about 9 bar, and it carries oils and tiny particles into the cup. Filter takes minutes, and only gravity.
The recipe is three numbers
Weigh the dry coffee going in (the dose) and the liquid coming out (the yield). Most cafés start near 1:2 by weight — 18 g of coffee into 36 g of espresso — in about 25–30 seconds, counted from when the pump starts.
Both numbers are weighed, and in grams, not millilitres: the foam swells and shrinks from bag to bag, so the same shot can look big or small in the cup.
18 g of coffee in, 36 g of espresso out. What ratio is that?
Answer: 1:2 — the dose in, the liquid out, both on a scale. It is where most cafés start, and where you taste before touching anything.
Why the grind is so fine
Half a minute is not long to get flavor out, so the grounds have to be fine. The bed pushes back like a doorman: the pump supplies the pressure, the grind sets the pace. Too coarse and it gushes, too fine and it chokes.
Espresso asks a lot of a grinder: one small step changes the shot. It asks something of you, too — knowing when to stop.
Stop the shot at 36 g.
Crema is not a verdict
Crema is foam. Gas left in the beans from roasting dissolves under pressure, then fizzes out as the shot leaves the basket, and the coffee’s oils and fine solids help hold the bubbles up.
What is crema actually made of?
Answer: Gas from roasting, fizzing out. Roasting gas. It dissolves in the shot under pressure and fizzes out as the coffee leaves the basket; oils and fine solids hold the bubbles up.
Admire it, then taste
Fresh beans make more of it; so do robusta and the double-walled baskets on many home machines. None of it proves the shot is good, any more than a moustache proves character. Admire it, then taste: the cup decides.
“I would weigh the shot and taste it; the crema, however handsome, is not consulted.”