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What Is Bypass Brewing?

Why adding water after brewing can open up new flavors.

by Ashley Rodriguez | January 27, 2022

A lot of coffee recipes are set up using ratios. A 1:16 ratio means that for every one gram of coffee you’d like to brew, you’d use 16 grams of water.

But what if you want to brew coffee for a crowd and you only have a small drip brewer? Or maybe you’d like your coffee to be just a tad bit less strong? Or what if you’re just a lover of coffee and want to explore how extraction and flavor works?

Bypass brewing is a technique used by coffee pros all the time to solve common brewing issues and explore the relationship between coffee extraction and strength. In this article, we’ll discuss how bypass brewing works and how to do it at home.

What is bypass brewing?

Bypass brewing is adding some of your brewing water directly into your final cup of coffee. Let’s say you’re brewing a cup of coffee with 30 grams of coffee and 500 of water — bypass brewing would use some of that water for actually brewing and pouring over ground coffee, and some of that water would be added to the coffee itself once brewing is finished. You’re literally bypassing the coffee grounds and skipping directly to the coffee mug.

If done correctly, bypass brewing is like adding an ice cube to a cup of whiskey or scotch: rather than diluting the coffee, it can open up your cup and make intense flavors less harsh.

Strength is a way to measure the total dissolved solids in your coffee, while extraction is what you actually take from the coffee during brewing.

Bypass brewing is a way to control the strength of your brew by manipulating the extraction of your grounds. Strength is a way to measure the total dissolved solids in your coffee, while extraction is what you actually take from the coffee during brewing. You can extract about 30 percent of a coffee bean, with most folks agreeing that around 20 percent extraction produces an ideal cup.

However, not all the flavors inherent in a coffee bean come out at the same time. “Fruit acids and caffeine dissolve the easiest, washing into the brew first. When isolated, this portion of the brew can taste bright and thin,” writes Sandra Elisa Loofbourow in her article, “Understanding Extraction.” After the fruit acids dissolve, then come fats and lipids, and after those are extracted come plant fibers and carbohydrates, which can add bitter, unpleasant notes in the cup.

Why use bypass brewing?

Bypass brewing can be used to isolate the flavors that come out during the first two phases of extraction and limit the bitter, papery notes that can come out towards the end. In fact, bypass brewing became so popular at the World AeroPress Competition that it was eventually banned.

After establishing the relationship between extraction and time, Loofbourow took her results and used them to understand bypass brewing, and found that grinding coarsely and bypassing produced the highest scoring coffee on the table, but did come with a tradeoff: those coffees couldn’t be diluted as much, so she was using the same amount of coffee grounds to yield about half the amount of actual brewed coffee. “Given the amount of work it takes to produce each bean,” she writes, “and the volume of coffee we want to drink on any given day, this doesn’t seem like a great solution.”

Instead, bypass brewing is a good technique to use to overcome specific obstacles. For example, bypass brewing is quicker than traditional brewing, so if you’re brewing a bunch of coffees back-to-back, this could be a handy trick. One of the reasons it’s popular to use on an AeroPress is that AeroPress brewers are really small and don’t have a ton of capacity to brew large batches. However, bypass brewing isn’t just for the AeroPress — it can be done with any brewer, and it’s especially handy if you’re brewing for a crowd.

You can also use bypassing to bring down the temperature of your coffee. Bypass brewing is a popular technique for iced (not cold brew!) coffee, where some of the water intended for brewing is instead replaced with cool water or ice. Usually, this is done at a 1:1 equivalency — if you have a 30:500 recipe, you might use 300 grams to brew and ice your brew with 200 grams of ice.

Anecdotally, I’ll bypass if my grind setting is too fine and I don’t want to extend my brew time nor do I want to start over. Rather than let water and grounds hang out and extract more and more from the coffee, I’ll sometimes pull the brew basket and dilute my coffee to my desired strength. This isn’t always ideal, but it’s one way to salvage a brew that hasn’t quite gone as expected.

How to bypass brew your coffee

First, determine how to split up your water. In Loofbourow’s experiments, she found that her tasting team preferred coffee brewed with 40 percent of the original brewing water. If we go back to our original recipe of 30 grams of coffee to 500 grams of water (which is a 1:16 brewing ratio), a bypass recipe would still use 30 grams of coffee, but only 200 grams of water to brew. It’s especially helpful to have a scale and a calculator for this.

Second, decide how much water you’ll add to the final brew. As you bypass, you might be tempted to add all the water you diverted from brewing into your cup — you do not have to do this. What’s lovely about bypass brewing is that you can control how much water you add. Try adding 10 percent of your water (in the 30:500 example, this would be 50 grams), taste, and add more if so desired.

Third, experiment with grind settings. Although Loofbourow’s tasting showed that a coarser grind was preferred by most of the tasters, that doesn’t mean you shouldn’t explore and try different grind settings of your own. Start with your preferred grind setting, and see what

As we mentioned above, bypass brewing is particularly popular with AeroPress brewing. You can find a catalog of winning recipes from the World AeroPress Competition here. The 2019 winner, Wendelien van Bunnik of the Netherlands, is especially active on social media and has shared her thoughts on bypass brewing on her Instagram account.