Without even knowing it, you've probably grown up with the sound of coffee grinding. Think about the coffee aisle in the supermarket, where large industrial grinders take whole beans and divvy them into small pieces. The practice of coffee grinding is so ubiquitous that it's even a bonus task on the television show Supermarket Sweep — both the original show and the newly rebooted version. Contestants can patiently grind a bag of coffee for extra cash.
Grinding coffee is an essential step in the brewing process, and with so many affordable options, it's a step you should consider taking out of the supermarket and into your home. Like many things at the supermarket, coffee is a food item that begins to get stale sooner if you grind it ahead of time. Grinding at home will allow you to enjoy the freshest, tastiest version of your favorite brew. Here's everything you need to know about how to grind for any situation.
Why the Grind Matters
Grinding makes coffee particles small enough so that when you pour water, it can extract flavor. If you simply throw whole beans into your coffee brewer, you'll end up with slightly coffee-flavored water, because the water can't penetrate the beans and find all the good-tasting stuff we're looking for. Grind size "ultimately impacts how water flows through the coffee bed, the corresponding extraction rate, and thus the final taste of the coffee you've brewed," says Sierra Yeo, the 2022 UK Brewers Cup Champion. Simply put, grinding coffee changes the available surface area for water to interact with coffee. The more surface area, the more water can mingle with, and pull flavor from, beans.
One way to think about grind size is to visualize how water would flow through a bunch of rocks versus sand. Sand particles are much smaller and have more surface area, so water would move through much more slowly than through rocks. Ground coffee is the same: The finer the grind, the more slowly water will move, and vice-versa. You might think then that you should grind your coffee as fine as possible, but, like Goldilocks, there's a sweet spot where you want to extract enough — but not too much — from your coffee.
Grinding isn't just about the size of your coffee particles but their shape and consistency. "The geometry of your coffee grounds, the average size of your ground particles, even the composition of differently-sized-and-shaped particles can affect the final flavor," says Yeo. Water will move through your coffee at different rates if you have particles in your brew that are all different shapes. Very finely ground particles might get too much of their flavor pulled out (this is where you'll get more bitter notes, what we call "over-extraction"), while coarser ground particles won't get enough of their flavor pulled out ("under extraction"). If you have both going on in your brew, it won't just even out — the coffee will taste both bitter and sour simultaneously.
Types of Grinders
There are hundreds of coffee grinders on the market, but most fall within two main categories:
Blade grinders: Blade grinders have a propellor-like blade, usually powered by a motor, that chops coffee into smaller pieces. However, blade grinders are notorious for chopping coffee unevenly, creating particles of all sizes. If you grind coffee with a blade grinder, you sort of never know what you're going to get: you might have particles that are dust-like in size, and others that look like giant boulders (sometimes a bean or two might even escape the blade, and not be chopped at all).
Burr grinders: Burrs are usually a set of plates that allow coffee beans to pass through, ensuring that they don't get "chopped" up again and making the resulting ground coffee much more even in size. Burrs can be made from stainless steel or porcelain, and you control the grind size by moving the burrs closer to, or further from, one another. Burr grinders can be automatic (you press a button, and it grinds) or manual (usually involving a crank one must turn).
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