One variable for the next brew

Coffee dial-in guide

Taste is preference, not a defect code. The coach separates strength from extraction only where the selected evidence permits.

Method
What did you notice?

Next controlled change

One change, chosen from what you tasted

  1. Tick what you tasted. Sour, bitter, weak: taste words are the starting evidence.
  2. Add what you measured. For espresso, dose, yield and seconds turn a guess into a move. Leave blank what you did not measure; nothing is filled in for you.
  3. Get exactly one move. A grind step or a ratio step, why, what to avoid, and the evidence it used.

Coming from Brew mode? Your brew is already loaded. Nothing you type here leaves this device.

Strength is not extraction

Strength is the concentration measured as TDS; extraction yield combines beverage mass, TDS and dose. Current SCA Brewing Chart research also shows that sensory attributes do not fit one universal sour/under or bitter/over zone. The coach is a transparent preference heuristic, not a diagnosis.

Conflict is an answer

If symptoms oppose each other, CupTune asks for another controlled brew instead of manufacturing a confident adjustment.

How the espresso rules work

Under 22 seconds at a 1:2 ratio counts as fast and over 35 seconds as slow. Those limits stretch in proportion when your ratio is longer or shorter. Sour and fast moves the grind one step finer; bitter or harsh and slow moves it one step coarser. With a normal time, the move is the ratio, in steps of 0.25. Every threshold here is a CupTune-authored rule of thumb, not a measurement. For the whole loop, step by step, read how to dial in espresso at home.

Bag age and missing numbers

Past 30 days off roast, the coach adds a freshness note and holds the grind when your evidence is inconsistent. A number you leave blank is treated as not measured and is never estimated; with too little data the coach says what to measure next.

When the cup tastes wrong

My coffee is sour — what should I change?

Sourness often indicates lower extraction, so a finer grind is the usual single-variable trial. The coach will say so, and will also say when the symptoms you ticked do not support that conclusion.

Why does the coach sometimes refuse to advise?

Because opposing symptoms do not identify one variable. When your notes conflict, CupTune asks for another controlled brew rather than manufacturing a confident answer.

Is bitter coffee always over-extracted?

No. Bitterness can come from over-extraction, from roast level, from very high strength or from uneven extraction, which is why more than one symptom is asked for.

How many things should I change at once?

One. Changing two variables between brews means the next result cannot tell you which one caused it, and that is the whole basis of the method.