Fix My Coffee
Why is my coffee sour?
Sourness almost always means under-extraction: the water did not pull enough out of the grounds. The fastest fix is to grind finer — two or three clicks.
Why it happens
The compounds in coffee do not dissolve at the same time. Acids come out first, then sugars, then the bitter compounds last. Stop extraction early and the acids dominate the cup: sour, salty, hollow. Grinding finer gives the water more surface to work on and lets extraction finish.
If finer does not fix it
Work through these in order: get the water to 92–96 °C; extend the brew time; add a gram of coffee. One at a time, not all at once.
It might just be too fresh
Coffee roasted less than five days ago is still releasing carbon dioxide. That gas keeps water off the grounds and the result reads sour. Do not change your settings for this — wait two or three days.
Sour or acidic?
They are not the same. A good Ethiopian coffee has a bright, lemony acidity, and that is the point of it. The sourness that is a fault tastes hollow and sharp next to it, and leaves no sweetness behind.
Fix My Coffee tracks this for you: rate a brew as sour and it tells you how much finer to go.