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The Coffee Troubleshooting Card

Six symptoms, one fix at a time.

Let the cup tell you what to change. Find the symptom below, try the first fix, brew again — and stop as soon as the problem resolves.

The golden rule: change one variable at a time, brew again, and stop as soon as the problem resolves.

Sour or sharp — under-extracted

Something moved too fast

  1. Grind finer (one step). The first and most effective fix.
  2. Still sour? Extend contact time — French press: +30 seconds. Pour-over & espresso: a finer grind is the time adjustment.
  3. Still sour? Slightly hotter water, staying inside 90–96°C (194–205°F).

Check first: actually sour, or just weak? Weak means faint and diluted — that's a ratio problem, not an extraction problem.

Bitter or harsh — over-extracted

Something moved too slowly

  1. Grind coarser (one step).
  2. Still bitter? Shorten contact time — French press: −30 seconds, and always decant immediately after pressing.
  3. Still bitter? Slightly cooler water, staying inside 90–96°C.

Brewing a very dark roast? Smoky-bitter may be the roast itself, not your technique — test with a medium roast.

Weak — a ratio problem, not extraction

Not enough coffee for the water

  1. Add 1–2 g of coffee, same water. (French press: 2–4 g, e.g. 30 g → 32–34 g at 480 g water.)
  2. Keep the grind exactly where it is.
  3. Re-taste before changing anything else.

Never grind finer to fix a weak cup — you'll get a cup that's still weak and now also bitter.

Dull or lifeless — a freshness problem

Usually upstream of your technique

  1. Fresher beans — look for a roast date and brew within about four weeks of it. No roast date on the bag is itself the answer.
  2. Grind just before brewing. Airtight container, in a cupboard — never the fridge.
  3. Then, if needed: a few degrees hotter, inside 90–96°C.

No grind, ratio, or time change can restore freshness already lost.

Thin or watery — a body problem

Adequate flavor, not enough texture

  1. Add 1–2 g of coffee.
  2. Still thin? Grind one step finer — the compounds that give coffee body dissolve mid-extraction.
  3. Check the clock: pour-over 2:30–3:30 · French press 4:00 steep · espresso 25–30 s. Finishing fast? A finer grind fixes the time and the thinness together.

If it persists after all three, reconsider the beans.

Inconsistent — a process problem

Great yesterday, flat today

  1. Weigh coffee and water. Every brew.
  2. Mark your grind setting and check it before each brew.
  3. Same steps, timer on, temperature checked — not estimated.

Control enough variables and the next off cup will tell you exactly what caused it.

The baselines behind every fix — 1:16 ratio · 90–96°C (194–205°F) water · one change at a time. Next tool: The Ratio & Grind Cheat Sheet.

The PDF versions

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The Coffee Troubleshooting Card, The Ratio & Grind Cheat Sheet and The Coffee Brew Log — the same three tools, laid out for paper so they can live next to your kettle. Leave your email and I'll send you all three.

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