Grinding and grinders

Why fineness changes everything

Grinding increases the surface of the coffee that the water touches. The finer the grind, the faster the water draws out flavours, but the slower it passes through the coffee. That is why every brewing method asks for its own fineness: short contact under pressure (espresso) needs a fine grind, and long contact without pressure (French press) a coarse one.

The scale, from finest to coarsest

• Turkish coffee: like flour. The coffee stays in the cup.
• Espresso: fine, a little finer than granulated sugar.
• Moka: a little coarser than espresso.
• Aeropress: from fine to medium, depending on the recipe.
• V60: medium-fine, like sand.
• Chemex: medium-coarse, because the thicker filter slows the flow.
• French press: coarse, like coarse sea salt.
• Cold brew: the coarsest, like coarsely ground pepper.

The comparisons are a rough guide, and the numbers on a grinder are not universal: “15” on one grinder is not “15” on another. So it pays to watch the coffee and the shot time, not the number. You will find an interactive scale with particle size ranges in the Lab.

Blades or burrs

A blade grinder does not grind, it chops. You get large and small particles together, and the result cannot be repeated. For espresso it does not work.

A burr grinder grinds the coffee between two burrs set a fixed distance apart, so the particles are more uniform. There are two kinds:

• Conical burrs: as a rule they turn more slowly and are often quieter. They tend towards slightly more fine particles and more body in the cup.
• Flat burrs: as a rule they give a more uniform particle and a cleaner taste.

These are tendencies, not rules: the differences between individual grinders are often greater than the difference between burr shapes.

Stepped and stepless

A stepped grinder has clicks. A stepless grinder turns continuously. For espresso the difference between two clicks is sometimes too big, so grinders that are stepless or have very fine steps are more pleasant to adjust.

Small things that make a difference

• Retention: some of the coffee stays in the grinder and comes out with the next dose. If you grind dose by dose (single dosing), choose a grinder that retains little.
• Static: a few drops of water on the beans before grinding (RDT) reduce static and clumping. A paper published in the journal Matter in 2023 confirmed this too.
• Change the grind while the grinder is running, if the manufacturer recommends it, so the beans do not jam.