Grind size, the master dial
Why grind size changes everything else — 5 min
Grind size is the variable the other four answer to. Grinding finer does two things at once: it multiplies the surface where water can work, and it shortens the distance to the center of each particle. Both speed up extraction — dramatically. That is why espresso needs powder and thirty seconds while a press needs gravel and four minutes.
In pour-over there is a third effect: finer grounds pack tighter and drain slower, so the grind also sets the contact time. One dial, three consequences.
Interactive
Drag the grind finer and watch how fast water can empty each particle.
Try it in the Blend app
No grinder produces one size. Every grind is a population: mostly the size you asked for, plus dust (fines) and oversized chunks (boulders). Fines over-extract and read as bitterness; boulders under-extract and read as hollow sourness. Better grinders make a tighter population — that is most of what you pay for.
The working rule you will use for the rest of this course: sour means grind finer, bitter means grind coarser — one step at a time, tasting between steps.
Note
This is why blade grinders frustrate: a spinning blade chops until you stop it, producing dust and chunks in the same batch — both flaws at once, in every cup. Burrs shear beans through a fixed gap, so the population clusters around one size you chose.
Brew it with a guided timer.
Blend counts the pour, times every step, and saves what you change. Free on iOS and Android.