Can Boiling Water Be Used to Brew Coffee? What's the Ideal Water Temperature for Pour-Over? Must It Be 92°C?

Can You Brew Coffee with 100°C Boiling Water?

During a daily brewing process, a customer asked FrontStreet Coffee a question: "Why doesn't anyone use 100°C boiling water to brew coffee?"

Water temperature, as a "tool" for adjusting extraction speed, is often the first brewing parameter many people focus on. Looking at all coffee brewing guides, water temperature recommendations fall within the conservative range of 86-93°C. Very few people use water below 80°C or above 95°C to extract coffee, because we know this can avoid over-extraction and under-extraction from a temperature perspective.

So what happens when you use boiling water to brew coffee? Practice makes perfect—without further ado, let's start brewing immediately!

Experiment Setup

For this experiment, FrontStreet Coffee divided it into two groups for comparison. Keeping all other parameters constant, we brewed using the corresponding regular temperature for each coffee and boiling water, making a total of four pots of coffee. Here, FrontStreet Coffee selected two coffee beans with different roast levels: a dark roast that presents rich bitterness and a light roast featuring fruit acidity.

Coffee Bean: Colombia · Dividing Line Large Navel (Medium-Light Roast)
Dose: 15g
Water Ratio: 1:15
Grind Size: EK43s setting 9.5
Dripper: Hario V60
Pouring Method: Three-stage pour

93°C Group: TDS 1.27% / Coffee Temperature 30°C

The coffee brewed with regular water temperature showed very full aroma, with not only a refreshing taste like blackcurrant juice but also delicate textures of blueberry and ripe hawthorn. The aroma and flavor persisted in the mouth, with acid preceding sweetness, creating rich layers that leave a deep impression.

Boiling Water Group: TDS 1.53% / Coffee Temperature 31.5°C

Compared to the regular temperature group, the Dividing Line Large Navel coffee brewed with boiling water presented fruit aromas of passion fruit and black grapes. The orange-like acidity was prominent and assertive, but lacked some fermented charm and spice notes of ripe fruits. While not as rich in layers as the previous group, the Large Navel brewed with boiling water can still be considered a decent fruit-acid type coffee.

Dark Roast Experiment

Next, FrontStreet Coffee selected a dark roast coffee bean for the second group brewing in this boiling water experiment.

Coffee Bean: Indonesia · Mandheling (Medium-Dark Roast)
Dose: 15g
Water Ratio: 1:15
Grind Size: EK43s setting 10.5
Dripper: KONO
Pouring Method: Three-stage pour

88°C Group: Concentration 1.38% / Coffee Temperature 29.6°C

The coffee exhibited Mandheling's chocolate and nutty aromas, with a creamy smooth entry, accompanied by the sweet aftertaste of Pu'er tea. The mouthfeel was clear yet rich, and even after the coffee cooled, no negative flavors appeared.

Boiling Water Group: Concentration 1.56% / Coffee Temperature 32.8°C

Due to the much higher water temperature than the first regular group, the coffee had a slight smoky aroma. The entry was dominated by bitterness and impurities, with obvious astringency on the tongue after swallowing, which reminded FrontStreet Coffee of an unripe green plum. After the coffee cooled, the entire cup of Mandheling once became "Chinese medicine soup," with burnt wood flavors filling the entire mouth.

The Science Behind Water Temperature

When we break down all parameters of pour-over coffee and temporarily set aside brewing techniques or flavors, discussing only the impact of water temperature on coffee extraction rate, the answer is obvious: the higher the temperature, the faster substances dissolve; the lower the temperature, the longer it takes for substances to dissolve. This also explains why when we want to speed up coffee extraction efficiency, we usually increase the water temperature by 2-3°C to extract more flavor compounds in the same time.

For light roast coffee, which is composed of various acidic components, higher temperatures more easily release strong acidic substances, so it's generally recommended to use high-temperature water between 91-93°C.

As the roast level deepens, various flavor compounds in coffee gradually undergo caramelization. Surface substances gradually develop characteristics of mellow sweetness, burnt aroma, smokiness, and richness—what we commonly call "coffee flavor." Unpleasant flavors also increase toward the end of extraction. Therefore, to avoid roasted bitterness taking over, we prefer to use slightly lower temperature water for extraction, typically in the 86-88°C range.

Conclusion

Through the above comparative experiments, we can see that whether it's dark roast coffee that presents rich sweetness or light roast coffee featuring fruit acidity, 100°C boiling water is clearly not an ideal brewing temperature. After all, compared to the reference water temperatures we usually use, boiling water is at least 7°C higher and up to 14°C higher than the standard. Consequently, the extraction efficiency for coffee naturally becomes much higher—in other words, acidic coffee becomes more acidic, and bitter coffee becomes more bitter.

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473