When you taste a cup of coffee, what’s the first thing that hits you? The potency of the flavors, or the flavors themselves? Do you taste nuance, sweetness, articulate notes that differentiate one coffee from the next? If not, don’t worry: It might not be that your palate has taken a vacation — instead, you might find that your brewing could use a little tweaking to get the extraction and strength just right.
“Strength” is a familiar word to pretty much all coffee drinkers, right? It’s one of the words used to describe the intensity of flavors that exist in a cup: The other one, “weak,” can leave us disappointed and longing for more… or at least, something? Anything??
While strength controls how much of the flavor we experience in a brew, extraction is what puts those flavors in there in the first place: We need to extract the good-tasting things from the coffee grounds first, and then make sure they’re in the right concentration to give us an exquisite coffee experience.
This combination — extraction plus strength — is part of the reason that making perfect coffee can be so darned hard, even though there are only two ingredients. The good news is that figuring out how to line up strength and extraction isn’t that hard, and all you really need to know in order to get it down pat are the three major variables that affect the relationship between extraction and strength.
(True coffee nerds will tell you that there are many more variables than the three, but trust me here: Three are key, and the rest are gravy.)
Everybody knows you have to get your recipe under control before you can make a decent cup of coffee, right? That’s why you know that the most commonly recommended ratio by brew nerds (like me and everybody else here at Trade) is 16:1, water to coffee. That means if you’re brewing 400 milliliters of water and using 25 grams of coffee, chances are you’ll be in the “good brew” ballpark.
Want to test your ratio? Easy: Brew and compare. Try making a batch with slightly more or slightly less coffee than usual — without changing any other variable — and see what your results are. Not only will one cup probably taste stronger and the other weaker, you’ll also probably start to detect some different flavors in each, as well.
Is the one with a smaller amount of coffee more bitter, with a long aftertaste? Those are some signs of overextraction — pulling too much coffee flavor out of the beans, which can happen when there’s too much water and not enough coffee. Is the other one kind of sour, with a drying aftertaste? That’s usually a tell-tale of underextraction – not pulling enough flavor out of the coffee, which can happen when the water is overwhelmed by how much coffee there is.
Great, you’ve got the first variable down! Now let’s start to get more complicated…
In addition to how much coffee and how much water you’re starting off with, you’ll want to consider your grind size. Think of it like this: When you’re roasting vegetables, you want to make sure all the pieces are cut to roughly the same size, right? That’s what a coffee grinder does to coffee beans. Now, consider that if you cut the vegetables smaller, they roast faster, and if you cut the vegetables real chunky, they roast slower — you follow me?
Coffee is kind of the same way. The finer your coffee grounds, the smaller the particles, the faster they will have stuff extracted from them. The coarser your coffee grounds, the slower they will have stuff extracted from them. This is because it takes water a bit longer to penetrate bigger, chunkier coffee grounds, where it can absorb right into the smaller ones and pull out what it wants.
Let’s put it together: If your recipe is still that 400 milliliters of water and 25 grams of coffee, but your coffee is ground fine, the water will extract more material from the coffee — which might taste both overextracted (bitter, long aftertaste) and too strong or intense. If you take that same coffee recipe and grind the coffee coarse, the water will struggle to extract material from the coffee, which means — bingo, you’re right! — sour, dry flavors and a weak, or less intense cup.
If you start with that 16:1 ratio but you’re still finding that your coffee is only “meh,” try adjusting the grind size a skosh in either direction and see if you wind up with something more articulate, with more natural sweetness in the cup.
Many people are afraid to change their grind size, as though for some reason it will be impossible to recapture the glory once the grinder has been touched. If this is you, don’t sweat it: Snap a quick photo of your current grinder settings before tinkering around, and if all else fails, you’ll be able to go back and act like all of this was just a weird fever dream.
The last (but not least) significant variable in the extraction trifecta is the contact time, which specifically refers to how long water and coffee are touching each other during the course of your brew.
For example: If you’re a French press fan, your contact time and your total brew time are the same, since all the coffee and all the water are touching for the duration of the four to five minute brew. However, when you’re brewing a pour over like a Chemex or a V60, or in your automatic drip coffee maker, the contact time will vary, because water is flowing into and out of the coffee grounds at a particular rate.
There are a few different ways that you can control your contact time, but the two simplest ones are, you guessed it, the ones we’ve already talked about: your recipe and your grind size. The recipe can affect contact time, because the more coffee you have in your filter, the longer it will generally take your water to flow through and out of it, extracting coffee material along the way. The inverse is obviously true as well: Less coffee means water can pass through the grounds quicker, and will extract less as a result.
You can also speed up or slow down the extraction and control the contact time by making the grind finer or coarser: Imagine pouring water through a sieve full of rocks and pouring water through a sieve full of sand; which one will the water flow through faster? The rocks, because there are larger gaps between them, and the water won’t get absorbed in them as easily.
What that means is you will ultimately need to get your coffee recipe and your grind size nice and calibrated in order to modulate your contact time. Again, this is where expert recommendations come in handy: Your favorite roaster probably has an idea of a recommended brew time somewhere on the coffee bag or on their website. But if not, a good rule of thumb is that espresso will usually fall somewhere between 20 to 30 seconds, most types of cone-shaped brewers will take three to five minutes (automatic drippers included), and immersion brews like French press are in the four to five minute range, give or take.
So… how are you feeling? Scared? Overwhelmed? Excited? Undercaffeinated? While it might sound complicated, there is really no one “right” way to properly brew, and the best results will always come from experimenting, comparing, and, of course, drinking lots of coffee — which we already know you can definitely handle, so go on ahead and get extracting!