Grind size

The grind size determines how much surface the coffee grounds offer the water and how quickly compounds dissolve. Finely ground coffee releases its compounds quickly, coarsely ground coffee more slowly. That is why espresso needs a very fine grind and a French press a coarse one.

If the grind is too fine for the method, the coffee tastes somewhat bitter and harsh; if too coarse, it tastes thin and sour. Even grinding with a good coffee grinder is important, and freshly ground coffee keeps more aroma than pre-ground.