Maybe you can relate to this: when I step into the kitchen first thing in the morning, what really starts waking me up is the incredible aroma of freshly-ground coffee. When they’re first ground into tiny particles, those little roasted seeds emit complex aromatic compounds that have been safely protected inside, as all that surface area is newly exposed to air and we breathe them in.
Sometimes, though, the amazing smells that pulled us from our morning haze into wakefulness are followed by a disappointing cup: either slightly sour and watery, or extra bitter and gritty. What happened?
It’s all about the grind size. The size and uniformity of those little particles are key factors for extracting flavor from coffee, no matter the method. Get the grind wrong, and your coffee will end up being over- or under-extracted – and you’ll be able to taste it.
We want you to enjoy your coffee at its absolute best. Here’s what you can do to make that happen.
Why does coffee need to be ground?
If you placed whole beans in hot water, we could extract some flavor over time. However, the result would be weak and watery, lacking the distinctive flavor of a cup of coffee.
But if we break the beans into smaller particles, we increase the surface area that interacts with the brewing water. This allows those beautiful flavor compounds to dissolve into the water more quickly and efficiently.
Why is grind size important?
The appropriate particle size for any given brew method is roughly proportionate to the contact time between water and coffee. Fast methods need a fine grind, and slow methods need a coarse grind.
No matter how we brew, flavor extracts from coffee in three distinct stages, always in the same order:
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Acidity
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Sweetness
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Bitterness
It’s useful to get a little science-y here. A roasted coffee seed is roughly 35% soluble in water. Put another way, it’s possible to extract about a third of the solids in that bean. However, the best flavor happens when we extract closer to 20%. That means there are soluble flavors in coffee that don’t actually taste very good! If we extract more than about 23% of the coffee solids, we’ll taste overly bitter, dirty, and ashy notes, as the extraction skews towards that third stage of flavor: bitterness. But if we don’t get at least 18% of the solids into our cup, our coffee will skew towards acidity, the first stage of extraction, and taste sour, watery, and astringent.
Choosing the right grind setting
We’ll repeat what we said above: The appropriate particle size for any given brew method is roughly proportionate to the contact time between water and coffee.
On one hand, espresso is a very fast brew method; we only have 20-30 seconds to grab flavor from a small amount of coffee. So we need a very tiny particle size, with plenty of surface area to provide for adequate flavor extraction.
On the other end of the spectrum, methods like French press or cold brew rely on considerably longer contact time, from 4-8 minutes for French press and up to 24 hours for cold brew. Because of that longer brew time, we don’t need nearly as much surface area for good flavor to extract; we can use a coarse, somewhat chunky grind.
And in the middle, we have percolation and drip methods (like the Hario V60s shown above), where water is moving steadily through a bed of ground coffee, picking up flavor as it moves. Depending on the exact brewing device and the water’s flow rate, we need somewhere between a medium-fine to medium-coarse grind.
Roast profile (light, medium, dark, very dark) matters too. You might find that you prefer a slightly coarser grind for darker roasts, because dark roasts are less dense and therefore more soluble, tending to overextract. Lighter roasts tend to be denser; you may need a finer grind to access the best flavors. The bottom line: taste, notice, and adjust.
Finally, consider the roast date. Ideally, you will be using freshly roasted beans, but as the days go by and your coffee gets older, you may need to tweak your grind again to get the flavors you want.
What about the grinder?
Generally, there are two types of grinders on the market: burr and blade grinders. Blade grinders aren’t actually grinders at all; they chop up beans using spinning blades. Like chopping a round fruit with a chef’s knife, you’ll never achieve uniform particle size. This affects taste, as the coffee particles are extracted at different rates because of their different sizes.
Burr grinders work by crushing the beans between two spinning burrs. Although these can be more costly, they are much more consistent (and what we recommend!).
The Baratza Encore is an electric burr grinder with 40 individual grind settings, and is suitable for nearly any brewing method, from home espresso to French press.
At the end of the day (or perhaps at the start of the day!), getting a handle on grind size will make a huge difference in your ability to craft tasty, consistent coffee. If you’d like to dive deeper into grind size and perfecting your coffee at home, join us for a class in the Learning Lab:
How to Brew Better Coffee at Home
How to Taste Coffee Like a Pro