Why Is Grind Size Important?

Why is grind size important?

Our grind size plays a vital role in how we brew coffee and significantly impacts the flavors we extract. Being able to adjust our grind size allows us to improve the quality of our cup, ensure that we can repeat the brew, experiment with extraction, create recipes, and more.

Burr vs. Blade Grinders

Burr grinders are the preferred tool for grinding coffee within the specialty coffee industry. They feature either conical or flat sets of burrs that grind your coffee with precision. Prices for burr grinders will vary, and there are models available for everything from home to professional use,. A burr grinder is a must-have piece of equipment to step up your brewing game.

Blade grinders produce an inconsistent grind size. Think of a tiny food processor chopping up all the bits until it’s so fine it can’t go any finer. There isn’t much control for precision or for the operator to control the grind size for optimum extraction.

Extraction & Flavor

There’s a certain goal we’re trying to reach when brewing coffee and when making changes to our brew variables. Ultimately, we want a balanced flavor profile in all of our brew methods including our espresso, pour-overs, or immersion brews. This is achievable through controlled extraction. 

The flavors in a cup of coffee will be the result of soluble compounds that we were able to extract through a balance of water to coffee ratio, grind size, water temperature, brew time, pour technique, and much more.

Below we will outline some guidelines we’ve put together to help find the correct grind size for your brew. We’re using µm (micron) as a measurement. If that’s a new measurement to you, don’t worry, we’ll expand on what some of these terms mean.

In our roastery, we use the Lighttells CM-200, which measures both roast color as well as grind size and uniformity. This is a helpful tool when we’re trying to match grind sizes across different grinders, or when we’re trying to determine how to brew a pre-ground sample of coffee.

400um

Fine – Turkish coffee, Moka pot, or espresso

600um

Medium Fine – AeroPress and siphon pot

800um

Medium – drip brewers or pour overs

1100

Medium Coarse – cupping and French Press

1400um

Coarse – cold brew

Grind Size Vocabulary – Sand And Salt?

You’ve probably read recipes that call for a grind size of “coarse sea salt” or “sand.” While this may have been helpful for some people, but the issue here is that many people can interpret this size differently. This makes calibrating across home brewers or commercial grinders difficult and frustrating.

In previous blog posts, we’ve explained that burrs and blades all vary in age, resulting in dullness over time. This will effect the consistency of our particle size distribution, resulting in an uneven extraction.

Imagine two different people are brewing coffee. One may be a using a commercial grade Mahlkonig EK-43 with 98mm flat steel burrs, while another may have a Fellow Ode Grinder with 64mm flat steel burrs, a grinder designed for home coffee connoisseurs. Each grinder will produce varying particle sizes, and we can use microns to measure grind and as a way to calibrate with others and dial in comparable brew recipes.

So how does grind size affect our brew?

Now we know to measure in microns let’s discuss how different micron sizes will affect our brew. The finer our grind size, the more surface area we have for extraction. We experience an increased contact time since our water has many more small particles to travel through. A coarser grind, like pebbles, will have shorter contact time, since there’s less surface area to extract from. This results in a cup that tastes brighter with a lighter body.

Finding the right grind size depends on a few factors. Your filtration method is a big one, since the filter serves as a barrier that keeps grounds out of your cup. The more open your filter is, the coarser your grind needs to be (the metal plunger on a French Press is a good example of a filter that requires a coarser grind size). Once you match your grind size to your filter, you can dial in the grind to taste. If your brew is tasting hollow, flat, or a little boring, try grinding a bit finer. If you’re finding your cup to be overly bitter or too syrupy, a coarser grind may help.

Stay tuned for more deep dives into brew variables, extraction theory, and brew alongs.