Extraction 101
Under vs over — and how to fix both.
The sweet spot
Extraction is how much of the bean dissolves into the water. Too little and it's sour; too much and it's bitter. The sweet spot is in between.
The scale
under sour, salty, thin → grind finer / longer sweet balanced, sweet → stop here over bitter, hollow, dry → grind coarser / shorter
Fix it fast
One variable at a time. Grind is the biggest lever — then time, then temperature.