Field Manual · Brewing
Ratios, grind and temperature for six methods — and how to read a bad cup and fix it.
Almost every bad cup of home coffee comes down to one of two things: the ratio or the grind. Fix those and everything else is preference.
Ratio: start at 1:16. One gram of coffee for every sixteen grams of water, or roughly 60 grams of coffee per litre. Weigh it. Scoops lie, because a scoop of coarse grounds and a scoop of fine grounds are different amounts of coffee. A $12 kitchen scale improves a home setup more than a $300 machine does.
Water: 195–205°F. Boiling water scorches the grounds. Water below about 190°F leaves the good parts behind. If you don't have a thermometer, take the kettle off the boil and wait thirty seconds.
Bloom with twice the coffee's weight in water for 30 seconds, then pour in slow circles. Keeps origin character intact — the best way to taste a single origin.
Most home machines under-dose badly if you use the scoop they shipped with. Weigh it once and mark the scoop.
Our Drip grind is too fine here and will silt the cup. Buy whole bean and grind coarse, or expect sediment.
Forgiving. Lower the water temperature to about 185°F for dark roasts to cut bitterness.
If the shot runs in under 20 seconds it's too coarse; over 35 and it's too fine. Adjust grind, not dose.
Dilute the concentrate 1:1 with water or milk. Dark roasts work best; bright single origins go flat.
Bitter, harsh, drying. Over-extracted. The water spent too long with the grounds or the grind was too fine. Grind coarser first — it's the biggest lever — then shorten the brew, then drop the temperature.
Sour, thin, salty. Under-extracted. Grind finer, brew longer, or use hotter water. People often read sourness as "too strong" and add more coffee, which makes it worse.
Flat and papery. Usually stale, not mis-brewed. Ground coffee goes dull within a week. If you're buying pre-ground a month at a time, that's the ceiling on how good it can taste.
Start at 1:16 by weight — 1 gram of coffee for every 16 grams of water, which is about 60 grams of coffee per litre. Go to 1:15 for a stronger cup or 1:17 for a lighter one. Ratios by volume are unreliable because grind size changes how much fits in a scoop.
Between 195°F and 205°F (90–96°C). Boiling water scorches the grounds and pulls out bitterness; water under 190°F under-extracts and tastes sour and thin. Off the boil for 30 seconds is close enough without a thermometer.
Bitterness usually means over-extraction — the water pulled too much out of the grounds. Grind coarser, shorten the brew time, or lower the water temperature. Bitterness is far more often a grind problem than a roast problem.
Sour, thin coffee is under-extracted. Grind finer, brew longer, or use hotter water. A sour cup and a bitter cup are opposite problems, so changing the grind in the wrong direction makes it worse.
Whole bean is at its best from about 3 days to 4 weeks after the roast date. Ground coffee starts losing aromatics within minutes and is noticeably flat after a week. Store it in an airtight container at room temperature — not the freezer, and not the fridge.