Chapter 03
The biggest lever you have
Grinding decides how much surface the water can reach and how fast it flows past. Get this roughly right and most recipes work. Get it wrong and none of them do.
A scale from fine to coarse
Grinder numbers mean nothing outside their own model, so learn the textures instead. Rub a pinch between your fingers and compare.
- Extra fineFlour-like. Turkish coffee.
- FineTable salt, slightly clumpy. Espresso.
- Medium-fineFine sand. Pour-over, moka pot, AeroPress.
- MediumRegular sand. Flat-bottom drippers, batch brewers.
- CoarseSea salt. French press.
- Extra coarseCracked pepper. Cold brew.
The two-line rule
Sour, sharp, thin, salty? The coffee is under-extracted. Grind finer.
Bitter, harsh, dry, hollow? The coffee is over-extracted. Grind coarser.
Move one small step, keep everything else identical, and taste again. Two or three brews are usually enough to land somewhere good.
Why it works
Water dissolves compounds from coffee in a rough order: bright acids first, then sugars and the heavier compounds that read as sweetness and body, and finally the bitter, astringent ones.
A finer grind exposes more surface and slows the water, so more of everything is dissolved. A coarser grind does the opposite. The aim is to stop in the sweet middle.
Burr or blade
A blade grinder chops beans at random, giving a mixture of dust and boulders. The dust over-extracts while the boulders under-extract, so the cup is bitter and sour at once and no adjustment can fix it.
A burr grinder crushes beans between two cutting surfaces set a fixed distance apart. The particles come out far more even, and that distance is something you can set, repeat and change in small steps. An inexpensive hand burr grinder will outperform any blade grinder.
If a blade grinder is all you have
- Grind in short pulses and shake the grinder between them.
- Sift out the finest dust with a kitchen sieve.
- Prefer immersion methods such as French press, which are more tolerant of uneven particles.
Good habits
- Grind right before brewing. Ground coffee loses aroma within minutes and is noticeably flatter after a day.
- Weigh the beans, not the grounds. Dose in, then grind, so nothing stale is left sitting in the hopper.
- Expect to re-adjust. As a bag ages it usually needs a slightly finer setting. A new coffee almost always needs a new one.
- Clean it occasionally. Old oils turn rancid. Brush the burrs every few weeks.