The best grinder in the world won’t guarantee you excellent coffee if you don’t understand how grind size impacts the brewed coffee. Mastering this crucial stage in the journey from bean to cup can take your home-brewed coffees from ordinary to amazing.
This ultimate guide to coffee grind size will prepare you to start brewing the best coffees to ever come out of your kitchen. Let’s get started by looking at the different varieties of grinders and the kinds of grinds they produce.
Blade Grinders Versus Burr Grinders
Grinders fall into one of two categories: blade or burr.
Blade grinders are a lot like blenders. Sharp blades spin around and shred the coffee beans into tiny pieces. Because of the way they grind up the beans, blade grinders have a couple of drawbacks. For starters, the blades tend to cut the coffee beans into uneven pieces, which has a major impact on the flavor of the finished coffee since the bigger chunks will extract at a different rate than the smaller ones (more details on this in the next section). The other issue is that blade grinders heat up as they’re grinding and that heat travels into the grinds, “pre-cooking” the coffee and also having an unwanted effect on the final brew.
For these reasons, many coffee aficionados have a strong preference for burr grinders. They grind by using two interlocking discs, usually made from ceramic or stainless steel, to pulverize the beans. The distance between the burrs, rather than the time spent grinding, is what determines the size of the coffee grinds, with no unwanted heat. Burr grinders produce grinds that are more consistent than what blade grinders produce, although there will still be some level of variance.
How Grind Size Affects the Brew
Coffee is both art and science, which is to say that the simple matter of how grind size affects the brew is really not so simple. There are always several factors at play, but let’s focus on two major ones: surface area and extraction time.
Imagine you’re holding a single coffee bean in your hand. If you were to cut it in half, the two pieces would provide a greater amount of surface area for water to travel over than just the single, uncut coffee bean. The more you cut up the bean into smaller pieces, the more surface area you create. And more surface area equals more opportunity for flavor to be extracted.
The result is that finer coffee grounds will extract faster than coarser ones because there is more “real estate” for water to travel over, drawing out compounds along the way.
Grind size also affects the length of time over which extraction takes place. Coarse grinds have more space between them, allowing water to pass through quickly, whereas fine grinds fit together much more tightly, slowing the water down so it spends more time in contact with the grinds.
So what exactly happens when you miss the mark on extraction, either pulling too little flavor from the grinds or too much?
The Taste of Failure: Sour, Salty and Bitter
This will come as a surprise to no one: improperly brewed coffee tastes bad. But it’s important to know the difference between under-extracted-bad and over-extracted-bad so that you can get a sense of where you went wrong and then tweak your grind size and brewing technique to improve on your next attempt.
Under-extracted coffee tends to be sour, acidic or even salty. This happens because the water wasn’t able to effectively extract and break down the compounds from the beans to create a balanced cup.
Over-extracted coffee has a bitter or hollow flavor that lacks nuance and depth. This is the result of too many of the beans’ compounds being extracted, ruining the flavor profile of the coffee.
How to Choose the Right Grind Size for Coffee
Here’s your cheat sheet to the most common brewing methods and the optimal grind size for each. Of course, there’s always room to experiment (and that’s one of the fun parts of brewing your own coffee) but in general, these guidelines will point you in the right direction.
Brewing Method: Turkish coffee
Grind Size: Super fine
Turkish coffee is intense and concentrated, so grinds that have a powdery or flour-like consistency are ideal. They produce the characteristic body of Turkish coffee and allow for peak extraction during the relatively short brewing time.
Brewing Method: Espresso
Grind Size: Fine
If you’ve ever watched an espresso shot being pulled, you know that this method is all about speed and pressure, so tiny grinds are the way to go. They provide the required resistance to the powerful stream of water being passed through the coffee bed and are optimal for the short brew time.
Brewing Method: Pour Over and Drip Machines
Grind Size: Medium
With the pour over method and traditional drip coffee makers, you want the water to pass through the coffee in a slow, measured fashion. You don’t want to make it too difficult for the water to go through, however, so a medium-sized grind is your best bet to hit your desired extraction level.
Brewing Method: French Press
Grind Size: Coarse
French presses brew coffee by soaking the grinds in water for a few minutes and then passing a filter through the coffee to separate out the coffee particles. Finer grinds would pass right through the sieve and leave you with a gritty beverage, so coarse grinds are better for this method.
Brewing Method: Cold Brew
Grind Size: Coarse
The slowest of all brewing methods, cold brew has the grinds sitting in water for an extended period of time. Bigger grinds have the necessary size and surface area for slower extraction and a complex but balanced flavor profile.