13 September 2026 · 3 min read
espresso feels temperamental, but there really aren't many mistakes, and each has a signature — in the cup and in the pour. let's go by symptom.
first, the recipe baseline
to have something to fix, lock a reference: the classic recipe is about 1:2 (18 g in, 36 g of drink out) in 25–30 seconds. change one thing at a time or you won't know what worked.
sour and sharp
a sour, hollow, «underdone» cup is under-extraction: you pulled too little. causes: grind too coarse, too little water (a short shot), low temperature. the fix is to grind finer — that's the main lever. the pour slows, extraction gets fuller, the acidity turns pleasant.
bitter and astringent
a coarse, dry bitterness and an empty «ash» in the aftertaste is over-extraction: you pulled too much. causes: grind too fine, too long a shot, water too long or too hot. the fix is to grind coarser and/or shorten the yield.
runs too fast (in 10–15 s)
the water found an easy path. causes: grind too coarse, too little coffee in the basket, a weak or uneven tamp. the fix: finer grind, the right dose for the basket, a level tamp with no tilt.
runs too slow or «spits»
barely flows, drips, sprays sideways. causes: grind too fine or an overfilled dose. the fix: coarser grind, less coffee.
channeling
the cup is sour and bitter at once, and thin jets or spray come from the portafilter — water punched a channel and passed unevenly. this isn't a grind problem, it's a puck-prep problem. fix it with even distribution of the grounds (fluff and level — a wdt needle) and a level, horizontal tamp. an uneven puck means channels no matter the grind.
an «ashy», burnt taste
beans too dark, water too hot, or a dirty group. check the temperature, flush the group, backflush — and remember that very dark roasts will taste bitter at any setting.
the system in a nutshell
sour — grind finer; bitter — grind coarser; too fast/slow — also grind and dose; and if it's sour-and-bitter at once with jets, that's channeling — work on distribution and tamp, not the grind. change one parameter at a time and espresso quickly becomes predictable.