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Can You Re-brew Under-extracted Pour-Over Coffee? Four Key Parameters for Perfect Pour-Over!

Published: 2026-01-28 Author: FrontStreet Coffee

Last Updated: 2026/01/28, Pour-over coffee has become part of most people's daily routine, whether at home or in the office. Whenever there's a moment to spare, coffee enthusiasts will brew a pot. However, frequent brewing inevitably leads to occasional mishaps, with coffee that's too strong or too weak being common "culprits" of these brewing disasters.

Pour-over coffee has become part of most people's daily routine, whether at leisurely home or in the office workplace. Whenever there's a free moment, coffee enthusiasts will inevitably brew a pot. However, frequent brewing inevitably leads to occasional mishaps, with over-extraction or under-extraction being common culprits. It's unpleasant to drink but wasteful to discard. When wanting to avoid waste without forcing yourself to drink it, we need to find other methods to improve it.

Over-extraction or excessive concentration is easy to solve—simply dilute the coffee through bypass (adding water) to make it more palatable. But when dealing with under-extracted coffee, things become more challenging. We can't exactly pour it into a pot and "reduce it over high heat," can we?

Then FrontStreet Coffee, while browsing online, came across this comment: Could we pour it back and re-brew for a second extraction? Upon careful consideration, it seemed worth trying. So today, FrontStreet Coffee will demonstrate and verify whether re-extraction is truly feasible!

Why Try This? What's the Principle?

Before conducting this experiment, FrontStreet Coffee wants to explain why it's worth attempting. To achieve a delicious cup of coffee, we need to use hot water to extract appropriate amounts of sweet, sour, and bitter flavor compounds from the coffee (bitter compounds should be present but not excessive). This process relies on four suitable extraction parameters: water temperature, grind size, ratio, and time.

Compared to technique and water quality, these four parameters are more important for beginners. Each parameter affects corresponding extraction efficiency, working in complementary fashion. When one parameter deviates and cannot meet extraction needs, it causes variations in the final coffee flavor, resulting in under-extraction. Under-extraction means flavor compounds from the coffee haven't been fully extracted, hence the low concentration and weak taste. In other words, many flavor compounds remain in the coffee bed. Therefore, if we pour this "lacking something" coffee liquid back and extract those flavor compounds still hidden in the coffee, wouldn't this cup become delicious?

However, before experimenting, we need to understand that after brewing, the original 90+°C hot water has become coffee liquid around 70°C, and its extraction efficiency is no longer as high. So friends need not worry too much about over-extraction—the probability is extremely low.

The Extraction Experiment

The necessary prop for our experiment is naturally a pot of under-extracted coffee! Such a prop is incredibly easy to obtain. For this experiment, FrontStreet Coffee used Kenya Assalia beans. We only needed to reduce extraction efficiency to obtain a pot of under-extracted coffee. By adjusting to a coarser grind, we produced 70°C coffee with 1.16% concentration, quite under-extracted with essentially no positive flavor expression—it could be described as coffee-flavored water.

So we poured 1/2 of the total liquid (100ml) back into the coffee bed for re-extraction, then combined this re-brewed coffee with the remaining coffee liquid, finally evaluating through tasting to determine if it was acceptable—if not, we could extract again!

This 1/2 portion of coffee took 30 seconds for re-extraction. When added to the remaining coffee liquid, we remeasured and found the concentration increased from 1.16% to 1.22%. The tasted flavor was much fuller than before, with tea-like and berry notes beginning to emerge! At this point it was already quite palatable, but FrontStreet Coffee was rather greedy, so we poured it back once more (again 1/2).

The concentration then rose to 1.25%, with caramel sweetness, dark plum, and cherry tomato flavors becoming quite distinct! This better suited FrontStreet Coffee's palate, so we stopped there~ Thus we can confirm that this method is indeed feasible. However, prolonged pouring causes coffee flavors to continuously dissipate during this time, so its flavor expression will be somewhat weaker. Therefore, when we can brew coffee properly, we should do our best to brew it correctly. Only when brewing mishaps occur should we resort to post-brew flavor adjustments. After all, this increases tasks, and the flavor isn't as excellent as brewing it right from the start—reducing trivial matters! Right?