Sour and bitter aren't random — they're direct feedback on extraction. Sour means under-extracted (not enough flavor pulled from the grounds); bitter means over-extracted (too much pulled, including compounds that taste harsh). Both point back to the same handful of variables.
01Check your shot time first
Before changing anything, time your next shot from the moment it starts pouring to when you stop it.
| Shot time | Likely result |
|---|---|
| Under 20 seconds | Under-extracted — sour |
| 25–30 seconds | Balanced target range |
| 35+ seconds | Over-extracted — bitter |
02Grind size — the first knob to turn
Tastes sour? Grind one click finer. Tastes bitter? Grind one click coarser. Change grind size alone, pull a shot, taste, and adjust again — don't change grind and dose at the same time or you won't know which one fixed it.
03Dose and ratio
A standard starting recipe is 18g of ground coffee in, 36g of liquid espresso out, in 25–30 seconds — a 1:2 ratio. If your yield runs well short of target, you're likely under-extracting; well over, you're likely over-extracting.
04Water temperature
Hotter water extracts faster and more completely; cooler water extracts less. If grind and dose are dialed in but the shot still leans sour, a slight temperature increase (1–2°F/°C if your machine allows adjustment) can help. Leaning bitter — try dropping it slightly instead.
05Bean freshness and puck prep
Beans more than 3–4 weeks past roast date taste flat and sour no matter how well you dial in the rest. Uneven tamping or a poorly distributed puck can also cause channeling — water finding a low-resistance path through the puck — which produces a confusing mix of both sour and bitter notes in the same sip.
Work through shot time first, then grind, then dose, then temperature — in that order. Most home baristas solve sour or bitter shots with grind size alone.