Dialling In: A Troubleshooting Guide

Taste it, name the problem, change one thing. A practical diagnostic flow for any brew method.

Dialling in is the process of adjusting a recipe until a specific coffee tastes its best. It goes faster when you separate two questions: is it extracted correctly? and is it the right strength?¹

Most of this page is practice: the procedures are what experienced brewers do, and they are consistent with the measured relationships between extraction, strength and taste, but the individual rules have not been tested one by one. Where a step rests on a study, it is cited.

Step 1 — Name what you taste

You taste	Likely diagnosis
Sour, sharp, salty, thin finish, "unripe"	under-extracted
Bitter, dry, astringent, hollow, "ashy"	over-extracted
Sour and bitter	uneven extraction (channelling, wide grind distribution)
Flat, dull, not much of anything	under-extracted and/or stale coffee / high-alkalinity water
Watery, tea-like, lacking body	too weak (ratio too wide)
Muddy, heavy, overwhelming	too strong (ratio too tight)

The first two rows are the classic control-chart descriptors¹, and trained panels in a 2020 UC Davis study confirmed them: sourness fell and bitterness rose as extraction increased, while strength changed the intensity of everything without changing that balance². The "sour and bitter" row is the signature of channelling in espresso, where part of the puck is over-extracted and part under-extracted³. The flat cup row is practitioner experience, and the water half of it follows from the effect of alkalinity on acidity⁴.

InteractiveTaste compass

Describe the cup and the map shows the region you're in and the single change that moves you toward the box. Strength and extraction are independent axes, so the fix depends on which one is off.

Under-extracted at a normal strength.

Do this: Grind finer.

Or raise temperature 2–3 °C, or extend contact time.

How this is computed: Regions follow the brewing control chart: extraction (EY) on the horizontal axis, strength (TDS) on the vertical, ideal box 18–22 % × 1.15–1.45 % for filter coffee. The sensory labels for each region are the SCA/Lockhart descriptors, supported by UC Davis panels that found sourness and bitterness track extraction while “strength” tracks TDS largely independently. Sources: [7] [2] [6] [1]

Sour and weak are frequently confused. The test: a sour cup makes you wince; a weak cup just doesn't do much. Adding a little water to a small sample tells you a lot — if it improves, it was strong; if it gets sourer, it was under-extracted.

Step 2 — Change one variable

Extraction levers, in order of how much they move things⁵:

Grind — finer to extract more, coarser to extract less. One or two steps at a time.
Temperature — 2–3 °C hotter to extract more; cooler for less. Remember that a 2020 study found temperature changes flavour mostly through the extraction it produces, not on its own⁶.
Contact time / agitation — longer steep or an extra stir to extract more; the opposite for less.

Strength lever:

Ratio — tighter (less water) for stronger; wider for lighter. Adjust after extraction is right⁷.

Change one, brew, taste, repeat. Changing two at once tells you nothing.

Method-specific cues

These are Cup Engineering practice, consistent with practitioner guidance⁸⁵.

Pour over. Drawdown time is your first signal. Faster than ~2:15 with a thin, sour cup: grind finer. Slower than ~4:30 with a bitter or astringent cup: grind coarser or reduce agitation. A bed that's crater-shaped or has dry high walls is uneven — swirl or stir after the bloom.

Espresso. Shot time at a fixed dose and ratio is a proxy for grind. Under ~20 s and sour: finer. Over ~35 s and bitter: coarser. Sour and bitter with uneven spurts: fix puck prep before touching the grinder; the 2020 espresso modelling study found that reproducibility depends on avoiding the channelling that fine, tightly packed pucks invite³. If grind adjustments seem to do nothing, the coffee is probably too fresh (heavy CO₂) or the burrs need cleaning.

AeroPress. Almost impossible to get wrong; use temperature as your main lever. 80–85 °C for dark roasts, 92–96 °C for light.

French press. If it's silty and bitter, grind coarser and don't plunge. If it's thin and sour, extend the steep — 8 minutes is fine.

Step 3 — Log it

Every brew is a data point. Note dose, water, grind, temperature, time, and a one-line taste impression. If you have a refractometer, add TDS and computed EY. After a dozen brews the patterns for a given coffee become obvious, and after a few coffees the patterns for your grinder and water become obvious too.

The calculator lets you see the predicted direction of any change before you make it, and each recipe page has a brew log where you can record the result.

The common traps

Chasing freshness. Coffee at 2 days off roast behaves erratically because of CO₂ (see freshness). Wait a week.
Adjusting for the last cup. Coffee changes as it ages; a setting from three weeks ago won't be right today.
Ignoring water. If nothing you do fixes a flat cup, test your water⁴.
Grinding too far from the target. If you're four or five steps off, none of the fine-tuning above will help — find the coarse-to-fine range where drawdown or shot time is reasonable first.