Why Use Different Temperatures to Brew One Pot of Coffee? What is Three-Temperature Variable Brewing? What Water Temperature Should You Use for Pour-Over Coffee?

Understanding over-extraction in coffee brewing

Over-extraction is a common frustration for many coffee enthusiasts. As we all know, when a coffee becomes over-extracted it develops obvious off-flavors and bitterness that make it hard to drink. The main cause is an excessive extraction rate, but this can arise in different scenarios. The reason for an excessive extraction rate may be overly extreme extraction parameters, or it may be an issue with the grind quality of your grinder.

Solutions for over-extraction

If the problem is overly aggressive parameters, we can lower the extraction rate by adjusting them. If over-extraction is caused by excessive fine particles from the grinder, however, it becomes hard to fix through parameter changes alone. It is not without solutions: FrontStreet Coffee believes that sieving out fine particles or using variable-temperature brewing are both excellent options. Since FrontStreet Coffee has already shared the pros and cons of sieving fine particles several times, we will not dwell on that today and will focus instead on variable-temperature brewing.

What is variable-temperature brewing?

Variable-temperature brewing, as the name suggests, means completing a brew using different water temperatures. This method mainly affects the temperature of the hot water during extraction, while other parameters can stay virtually unchanged. We need to understand, though, that "different temperatures" here does not mean small differences of 2-3°C but a significant temperature range.

The origins and principles of variable-temperature brewing

The first person to invent and use this method was Mr. Wu Zelin from Taiwan, who won the World Barista Championship in 2016 using the technique. It was because of that achievement that variable-temperature brewing became known to the world. When water temperature is higher, its extraction efficiency increases and flavor compounds dissolve more easily; conversely, when water temperature is lower, extraction efficiency decreases and flavor compounds dissolve more slowly. Variable-temperature brewing uses this principle by dividing the hot water for a brew into two (or possibly more) different temperatures, thereby controlling how much is extracted from the grounds at different times. The exact timing of the temperature changes can therefore be adjusted to our needs.

Different approaches to variable-temperature brewing

Mr. Wu Zelin's approach, for example, divided the pour into four segments (16g of coffee, 1:15 coffee-to-water ratio, with segment water amounts of 40, 80, 80, and 40 ml respectively). The first two segments used 94°C water, while the last two used 90°C and 80°C respectively, creating a step-like temperature change. The advantage is that it extracts sweet and sour compounds intensively in the early stages while using relatively cooler water later, when bitter compounds are about to be released in large quantities, thereby slowing their dissolution. Because the release of bitter compounds is inhibited, the coffee shows more outstanding sweet and sour characteristics. Meanwhile, the method used by Emi, the 2018 WBrC champion, involved a smart dripper and a three-stage process: a low-temperature bloom and steep at 80°C, followed by high-temperature drip extraction at 95°C, and finally a low-temperature steep at 80°C before opening the valve to finish. This aims to reduce the release of acidic compounds, making the whole cup smoother with heightened sweetness.

How to implement variable-temperature brewing

We could follow the competitors' approach and use multiple temperature-controlled kettles to get different water temperatures at once, but that is obviously too extravagant, as it requires equipping several brewing kettles. FrontStreet Coffee therefore recommends using cold water to adjust the temperature during brewing. That way, one kettle is enough for variable-temperature extraction. The only drawback is that this method is limited to variable-temperature brewing where the temperature decreases from high to low.

The "Devil's Brewing Method"

Among the various variable-temperature methods, one FrontStreet Coffee especially favors is the advanced version of Mr. Tetsu Kasuya's 4:6 method, known as the "Devil's Brewing Method." The general process divides extraction into three segments: the first two use high-temperature water at 92°C for drip extraction, while the last uses low-temperature water at 70°C combined with immersion extraction. Because the final segment's water temperature is very low (relatively speaking), this method offers very high fault tolerance, making it easy to brew a cup that is high in sweetness and free of bitterness.

Demonstration with natural ALO coffee

The reason for favoring this method is simple: since we are already using something as extreme as variable-temperature brewing, why not add some flair so the effort feels worthwhile? So FrontStreet Coffee will use the "Devil's Brewing Method" for today's demonstration. The bean selected is the newly arrived natural-processed ALO, which under conventional brewing typically shows rich magnolia, citrus, and pineapple notes. The extraction parameters are as follows:

Coffee dose: 15g
Coffee-to-water ratio: 1:15
Grind size: EK43 setting 9, with 85% pass-through rate on a #20 sieve
Brewing method: Devil's Brewing Method
Dripper used: Hero variable-speed dripper
Water temperature: 92°C, 70°C

First, we pour 30ml of hot water for the bloom. The time is also thirty seconds, with the dripper valve kept open.

After the bloom, we use a small water flow in a circular motion to pour 60ml of hot water.

Once the pouring is complete, we immediately add room-temperature water to the kettle to lower the water temperature to 70°C.

When the hot water has finished penetrating, we close the valve and immediately pour the remaining 135ml of hot water in one go.

After steeping for thirty seconds, we can open the valve to release the coffee.

When the coffee has finished draining, we can remove the dripper and end the extraction.

Results and conclusion

Total time: 2 minutes and 41 seconds. This cup of variable-temperature-brewed ALO is easy to drink because of its moderate temperature, and its flavor profile is equally outstanding: mango, pineapple, and citrus with a very full, juice-like texture. If you frequently run into over-extraction from too many fine particles, trying variable-temperature brewing may well be worth it.

FrontStreet Coffee Recommendation

When over-extraction comes from too many fine particles, a bean whose flavors stay clear at low temperatures helps most, and FrontStreet's Ethiopia range shows its sweetness even in a cooler cup. The washed Gududing Cooperative of Yirgacheffe brings citrus, berry, and floral notes with a green-tea sweetness, while the sun-dried Huakui leads with strawberry, passionfruit, jackfruit, and lychee aromas, sweet and smooth with very little bitterness.

If you want a slightly darker, more chocolatey coffee that still handles a long, slow extraction gracefully, the FrontStreet PWN Golden Mandheling is roasted dark for very low acidity and a full, lingering body, with layers of herbal and dark chocolate aroma and a faint earthy note, suitable for those who like a heavy cup without sourness. Practicing a variable-temperature pour on either style lets you shorten the cool final stage without losing the flavor you came for.