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The Impact of Blooming and Its Duration on Pour-Over Coffee (Part 2)

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Last time, we used the Clever dripper to obtain objective data about blooming and its duration. We learned from sensory evaluation that as blooming time increases, acidity decreases while sweetness and viscosity are enhanced. The overall flavor profile gradually shifts toward the backend and becomes more complex. From the TDS and EXT readings, we observed that as blooming time lengthens, both TDS and EXT values show a downward trend. And I...

Last time, we used a Clever Dripper to obtain objective data about whether to bloom and for how long. We learned that as the bloom time increases, acidity decreases, while sweetness and viscosity are enhanced. The overall flavor profile gradually shifts backward and becomes more complex. From the TDS and EXT readings, we observed that as bloom time lengthens, both TDS and EXT values show a downward trend. We also mentioned that the Clever Dripper is closer to immersion brewing, so in this experiment, we'll apply the same method to a V60 dripper to see what kind of flavor profile and data it produces when using water flow agitation in this filter-style dripper.

Pour-over Experiment Design

The pour-over experiment was divided into two groups. The first group had a fixed brewing time of 2 minutes and 10 seconds, with bloom times of 0 seconds, 20 seconds, 40 seconds, and 60 seconds respectively. The second group considered that with different bloom times but the same total brewing time, when reaching 60 seconds of bloom, we would need to use a large water flow for rapid brewing to achieve the target 2 minutes and 10 seconds. This would mean that as bloom time extends, our subsequent water pouring would accelerate, and we all know that pour-over coffee with slow, fine water flow versus fast, large water flow produces very different flavor profiles. Therefore, we decided to add a second group of experiments to make the final data more objective. The second group still used bloom times of 0 seconds, 20 seconds, 40 seconds, and 60 seconds, but the total brewing time was extended accordingly as the bloom time lengthened.

Experiment Steps and Data

Pour-over Experiment 1

Pour-over experiment groups 1 and 2, using approximately 40g of water for blooming

(Both groups of pour-over experiments used approximately 40g of water for blooming)

Experiment Steps:

Weigh 15g of coffee beans, grind with Fuji (ghost teeth) #2 and set aside
Prepare sufficient 90°C hot water
A: Add 15g of coffee grounds to a Hario V60 conical dripper, continuously pour 240g of hot water in circular motion, total brewing time is 2min10s
B: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 20-second bloom, then pour 200g of hot water in circular motion, total brewing time is 2min10s
C: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 40-second bloom, then pour 200g of hot water in circular motion, total brewing time is 2min10s
D: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 60-second bloom, then pour 200g of hot water in circular motion, total brewing time is 2min10s

Experiment Results:

Results Analysis:

After comparative analysis with pre-experiment predictions, we found that as bloom time increases, the changes in flavor and mouthfeel generally follow expectations, showing decreased acidity with enhanced sweetness and viscosity. The overall flavor profile gradually shifts backward. The overall extraction rate results show a sequential decrease, which aligns with predicted results.

Cause Analysis:

In pour-over drip brewing, bloom time, brewing time, and coffee bed temperature (i.e., actual brewing temperature) collectively influence the overall extraction rate and cannot be considered in isolation. In this series of experiments, the actual extraction time and coffee bed temperature had relatively significant impacts on the results.

Pour-over Experiment 2

Second group of pour-over experiments showing extended brewing times with longer bloom periods

(Second group of pour-over experiments: as bloom time extends, total brewing time is extended accordingly)

In the previous pour-over experiment, the total brewing time was fixed, meaning that when bloom time increased, actual extraction time decreased. The following experiment will explore the effects of blooming or not, and bloom duration, on brewing results when maintaining consistent pouring speed—meaning the actual extraction time remains the same across all groups.

Experiment Steps:

Weigh 15g of coffee beans, grind with Fuji (ghost teeth) #2 and set aside
Prepare sufficient 90°C hot water
A: Add 15g of coffee grounds to a Hario V60 conical dripper, continuously pour 240g of hot water in circular motion, total brewing time is 1min58s
B: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 20-second bloom, then pour 200g of hot water in circular motion over 1min38s, total brewing time is 1min58s
C: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 40-second bloom, then pour 200g of hot water in circular motion over 1min38s, total brewing time is 2min18s
D: Add 15g of coffee grounds to a Hario V60 conical dripper, first pour 40g of hot water for 60-second bloom, then pour 200g of hot water in circular motion over 1min38s, total brewing time is 2min38s

Experiment Results:

Results Analysis:

In this series of experiments, as bloom time increased, the changes in coffee flavor and mouthfeel followed similar trends to the previous experiment. For overall extraction rate, however, it first decreased then increased. This shows that: 1. As bloom time extends, it causes the coffee bed temperature to drop, affecting the actual extraction temperature and decreasing extraction efficiency; 2. It's evident that as bloom time extends and actual extraction time correspondingly lengthens, increased bloom time can, to some extent, increase extraction efficiency, with the increase compensating for or even exceeding the extraction efficiency loss caused by the drop in coffee bed temperature.

Practical Applications and Conclusion

We conducted these several groups of experiments to gain a more detailed understanding of blooming. If you're interested, you can actually do rough experiments when brewing coffee yourself, trying different bloom times to experience their effects on mouthfeel. Understanding these data and flavor changes can also be applied to your daily pour-over coffee brewing. If you want prominent acidity with forward-facing flavors, you might consider not blooming or using a short bloom time. If you want a balanced, solid mouthfeel, you might consider blooming for a longer period.

Many customers directly ask us how long to bloom when brewing coffee, how long to brew, and what water temperature to use. What we fear most is giving rigid, fixed rules or answers. There are so many varieties of coffee beans, and each roaster's style is so diverse—how could we possibly brew all beans with just one method? How boring! Of course, if you want to do that, it's not entirely impossible. We often say that good beans aren't limited by brewing methods, but while there are many methods, there's always one that's most suitable for that particular bean, or perhaps your favorite flavor profile. Trying more can be quite interesting.

Pour-over experiments have always been something we find quite challenging because there are too many variables—it's so exaggerated that even a breeze blowing nearby seems to affect its taste. We originally thought we could quickly organize this experiment following up on last time, but the result was that we had to repeat it several times!! Actually, repeating several times isn't a big deal—at worst, our operator Xiao Hei would be more tired, but the point is that after each brew, we still had to do sensory evaluations, drinking until we were dizzy. Before noon, the three of us were already wandering around the store in a daze! Fortunately, this is what we love! We also hope the resulting data will be useful to everyone.

Next, we'll continue to play seriously and rigorously, diving deep into the coffee world to explore thoroughly. If you have any questions or curiosities, you can raise them with us. As long as our equipment and resources allow, we'll try experiments to provide answers.