QUESTION: What grind Is best for Chemex? I just received a 6 cup classic Chemex coffee maker as a gift, but I’m not sure how fine or coarse I should grind the beans. Which grind size will work the best in my new Chemex?
ANSWER: Your coffee beans should be ground to medium-coarse if you will brew your coffee in a Chemex. A Chemex arrangement can be fussy to work with, so make sure to grind the coffee beans so they’re between medium and coarse.
Getting the Right Grind for Your Chemex
Medium-coarse ground coffee beans should have a texture something like coarse sand or sea salt. Coffee that’s been ground for a Chemex should be a bit finer than coffee ground for a French press. However, note that we said the texture should be like coarse sand, not too fine, like the more finely textured standard sand.
If your grind setting is wrong (or something else is wrong), you’ll end up with coffee that’s over-extracted or under-extracted.
Under-Extraction Versus Over-Extraction
If the beans are not ground finely enough, your cup of coffee will be under-extracted. You’ll also notice that the coffee moves through the Chemex too quickly if the grind setting is too coarse.
If the coffee beans are ground too finely for the Chemex, your coffee will be over-extracted. When the coffee is ground too finely, it will clog the filter and take a long time to move through the Chemex.
Beans that are ground correctly (medium-coarse) for use in your Chemex will give you a perfectly balanced cup of coffee that’s neither over- or under-extracted. The brewing time and the level of extraction will complement one another, resulting in delicious coffee.
When the coffee is moving steadily through the Chemex with the right level of extraction, it should take between three and a half and four and a half minutes to brew. If your brew is moving too quickly, start over and try grinding the coffee beans more finely. If your brew is taking too long and moving too slowly, try a coarser grind setting.
You can tell a lot about whether a cup of coffee’s grind setting and extraction level are balanced just by tasting the brew. If the coffee tastes weak or you pick up sharp, acidic or sour flavors—or even a salty taste—these elements point to under-extraction, or coffee beans that are ground too coarsely.
On the other hand, over-extracted coffee can have very pungent and overwhelming flavors like bitterness or a burned taste. If your coffee is over-extracted, you won’t be able to detect any of the nuanced elements of the coffee beans.
Burr Grinders vs. Blade Grinders
Many of our sources recommended using burr grinders instead of blade grinders. If you’ve been using a blade grinder on your coffee beans, you’re not alone. Lots of other people use blade grinders instead of burr grinders—but that doesn’t make it the right choice. One of our sources even said that using a blade grinder on coffee beans is worse than just buying the beans pre-ground.
For one thing, blade grinders do not make the coffee grounds a consistent size. Some will be much finer than others, which means the level of extraction will differ with each erratically sized coffee ground.
Another problem with blade grinders is the friction and heat caused by the speed at which those blades are spinning. The heat actually begins the cooking process for your coffee grounds. As a result, the taste of your coffee will suffer, and the beverage will be overcooked by the time it’s finished brewing.
Burr grinders, on the other hand, can grind your beans completely consistently, so all the granules are of equal size. And because burr grinders work at lower temperatures than blade grinders, the problems you see in blade grinders because of friction and heat aren’t a concern. With espresso, the problems with blade grinders will be even more noticeable in the taste of the beverage than with coffee.
If we’ve convinced you to go ahead and purchase a burr grinder, look for a conical burr grinder. Either a hand grinder or an electric grinder will be fine, as long as it is a conical burr grinder.
Now you’ve learned about which grind size to use in your Chemex (medium-coarse). You’ve also found the information that’s necessary to help you analyze and tweak the settings of your coffee, like grind size or brew time, so you end up with your perfect cup of java.
Learn More About Chemex Coffee