Unimodal vs bimodal distribution

Two shapes of grind particle distribution. Unimodal has a single peak — most particles are at one size. Bimodal has two peaks — a lot of fines and a lot of target-size particles, with fewer particles in between.

Why it matters — Flat burrs tend to produce unimodal distributions (often called "cleaner" or "clearer" in the cup). Conical burrs tend toward bimodal (often called "sweeter" with more body). Neither is intrinsically better — they're different flavour profiles.

Good to know

• Don't assume flat = better. Plenty of café espresso is built around conicals (Mazzer Robur, Mahlkönig K30) for the body they produce.
• For filter coffee, unimodal usually wins for clarity. For espresso, the choice depends on the cup style you want.