Answer firstThe golden numbers for a good espresso: 18g in → 36g out (1:2), 25–30s, 9 bar, 92°C. Crema (the golden layer) is emulsified oils plus CO2 from fresh beans, a freshness sign, not proof of quality.
Espresso & crema cheat sheet
The golden numbers
18g
Dose (in)
36g
Yield (out)
25–30s
Shot time
9 bar
Pressure · 92°C
18g in · 36g out · 25–30s · 9 bar · 92°C
The golden ratio, 1:2
A 1:2 ratio (18g in, 36g out) is the balanced espresso starting point. Thicker and sweeter → 1:1.5 (ristretto); lighter and longer → 1:3 (lungo).
18g → 36g, a balanced 1:2 start
Where does crema come from?
Nine bars of pressure emulsify the coffee oils, and CO2 from fresh beans joins them to form that golden crema. So fresher beans give more, longer-lasting crema.
9 bar + 92°C + oils + CO2 = crema
The crema equation (and the myth)
Crema = emulsified oils + CO2. But remember: crema is a freshness sign, not proof of quality. Robusta makes thick crema yet tastes harsher. Don’t sacrifice flavour for crema.
Crema = freshness sign, not quality proof
Crema look
Means
Thick, golden
fresh, balanced
Pale, flows fast
under-extracted
Dark, spotty
over-extracted / too fine
· · ·
Pulling the shot
1. Fix the dose 18g, target yield 36g. 2. Set 9 bar, 92°C. 3. Time 25–30s. 4. Read the crema and taste to adjust. Too fast → grind finer; too slow → coarser (one change at a time).
18g in → set → 25–30s → 36g out, read the crema
Espresso feel (distribution, tamping, reading the flow) is fastest to learn on a real machine. JWC classes start with one dialed-in shot.
FAQ
Is more crema better?
No. More crema doesn’t mean better coffee; robusta makes lots but tastes harsher. It’s a freshness sign, not quality proof.
Why no crema?
Stale beans (CO2 gone) or too coarse a grind.
Do I have to dose 18g?
It depends on your basket; the key is a consistent dose and a target yield around 1:2.
How to fix the time?
Too fast, grind finer; too slow, coarser. One change at a time.
A dialed-in shot
Want a repeatable espresso at home?
From distribution and tamping to reading the flow, hands-on · from RM199 · real machines
