Grinding Coffee Right: Why Grind Size Changes Everything

Why Grind Size Changes Everything

You can buy the best beans in the world. Freshly roasted, single origin, 87 SCA points. But if you grind them wrong, your coffee will still taste disappointing. Grind size is one of the most important variables in coffee brewing - and the most underestimated.

The principle is simple: the finer you grind, the more surface area comes into contact with water. More surface means faster and stronger extraction. Ground too fine, the coffee turns bitter and over-extracted. Too coarse, and it tastes watery and sour - under-extracted. The sweet spot lies in between.

The Chemistry Behind Extraction

Coffee contains hundreds of flavor compounds, and they don't all dissolve at the same rate. Acids are extracted first, then sugars and sweet flavors, and finally bitter compounds. If you brew too short or too coarse, you only get the acids. If you brew too long or too fine, you also pull out unwanted bitterness. The goal: a balanced extraction where acidity, sweetness, and bitterness are in harmony.

The Key Grind Sizes at a Glance

Extra coarse (like coarse sea salt): For cold brew. The coffee steeps in cold water for 12 to 24 hours. Because the contact time is so long, the grind must be very coarse, otherwise the result becomes unpleasantly bitter.

Coarse (like flaky sea salt): For French Press. The metal mesh method needs coarse grounds so fine particles don't slip through the filter. Brew time: 4 minutes.

Medium-coarse: For Chemex and large pour-over filters. The Chemex has a particularly thick paper filter that drains more slowly. A slightly coarser grind compensates for that.

Medium (like table salt): For standard drip coffee and smaller pour overs like the Hario V60 with a medium flow rate. This is the all-rounder grind size.

Medium-fine: For AeroPress. The short brew time of 1 to 2 minutes needs a bit more surface area so enough flavor makes it into the cup.

Fine (like powdered sugar): For espresso. Hot water is forced through the compact coffee bed at 9 bars of pressure - in just 25 to 30 seconds. For this to work, the grind must be very fine and extremely uniform.

Extra fine (like flour): For Turkish coffee. Almost powder. The coffee is drunk unfiltered, and the grounds settle at the bottom of the cup.

Why Consistency Matters More Than Fine or Coarse

A grinder that produces uneven particles creates too-fine and too-coarse particles simultaneously. That means: part of your coffee is over-extracted (bitter), another part is under-extracted (sour). In the same cup. You taste both - and neither is good.

That's why the grinder matters so much. A cheap blade grinder chops beans more or less randomly. Particle size varies wildly. A burr grinder, on the other hand, grinds consistently and with control.

Blade Grinder vs. Burr Grinder

A blade grinder costs 20 to 30 Swiss francs and works like a blender: rotating blades chop the beans. The result is a mix of dust and coarse chunks. For specialty coffee, that's not ideal.

A burr grinder uses two grinding discs that press the coffee between them. You set the distance - that determines the grind size. The result is significantly more uniform. Good hand-operated burr grinders start at around 50 francs (e.g., Timemore C2 or Hario Skerton). Electric models start at 100 to 150 francs (Baratza Encore, Fellow Ode).

The difference in flavor is immediately noticeable. Not subtle, not "maybe I taste something." Clear and obvious.

Grinding Fresh Makes the Difference

Whole beans hold their aroma much longer than pre-ground coffee. As soon as coffee is ground, the surface starts to oxidize - volatile aromas dissipate within minutes. That's why the rule is: always grind just before brewing. Never in advance. The difference between freshly ground and pre-ground coffee is enormous.

Finding the Right Setting

Every coffee is different. Light roasts are harder and denser - they often need a slightly finer grind than darker roasts. Freshly roasted coffee (less than a week after roasting) still outgasses CO2, which affects extraction. And water hardness plays a role too.

The best approach: try, taste, adjust. Does your coffee taste too sour and thin? Grind finer. Does it taste bitter and flat? Grind coarser. Over time, you develop a feel for it. That's part of the ritual.

At Roestpost

Every week you get a new coffee from a different Swiss roastery. And each coffee brings its own personality - including when it comes to grind size. Experiment, explore, find your sweet spot. Subscribe now and make a new discovery every week.