Daily Brewing | Does the 30-second bloom time start counting from the beginning of water pouring or only after all water has been poured?

Professional Coffee Knowledge Exchange | For more coffee bean information, please follow Coffee Workshop (WeChat Public Account: cafe_style)

Today, a visiting enthusiast raised a question for the editor: When exactly does the bloom timing start - from the beginning of water pouring or only after pouring is complete?

Indeed, this is one of those oversight questions. While I often recommend blooming for about 30 seconds, I forgot to explain when exactly to start timing.

Well, today I'll make up for this omission and explain the issue of "bloom timing."

First, let me clarify: In all my videos, brewing demonstrations, and recommended parameters, I start timing only after water pouring is complete. Taking our most common brewing example of 15g coffee, we typically pour about 30g of water with a bloom time of 25-35 seconds.

For unconventional bloom pouring techniques (though I haven't discussed this topic much yet), it's usually noted as pouring time + bloom time. In any case, the time spent pouring is not counted as bloom time. Pouring and blooming are separate processes with separately calculated times.

The image above shows my demonstration of the normal pre-bloom pouring process. I pour 30g of water in about 10 seconds. This means that timing starts after pouring is complete: 10 seconds pouring + 30 seconds blooming = 40 seconds total. If we started timing from the beginning of water injection, then 10 seconds pouring + 20 seconds blooming = 30 seconds total, which would be 10 seconds less than my standard 30-second bloom recommendation.

The Impact of Bloom Duration on Pour-Over Coffee Extraction

So the question arises: how much impact does a 10-second difference in bloom time actually have on pour-over coffee extraction?

An Experimental Comparison: 20-Second vs 30-Second Bloom

Experimental variety: Yemen Mocha Mattari, Roast level: Medium; Roast date: June 28th, bean resting period: 11 days, essentially at peak flavor development.

Experimental method: Clever Dripper filter cup, placed on server during bloom pouring for both upper and lower circulation, simulating normal filter cup bloom pouring. After bloom completion, the server was removed and the plunger closed for immersion extraction to minimize the impact of subsequent pouring technique variations on extraction.

Experimental parameters: 15g coffee, total water 225g, water temperature 90°C, immersion extraction for 1 minute 40 seconds then returned to server for filtering, total extraction time 2 minutes. (All timing starts after pouring is complete)

Experimental Group ①: 20-Second Bloom

This group simulates timing 30 seconds from the beginning of pouring, with 30g water poured over 10 seconds + 20 seconds bloom. After bloom completion, the server was removed and 195g of water added.

Experimental Group ②: 30-Second Bloom

This group simulates timing 30 seconds after pouring is complete, with 30g water poured over 10 seconds + 30 seconds bloom. After bloom completion, the server was removed and 195g of water added.

Analysis

1. First, observing the surface during bloom: at 20 seconds, the coffee bed surface still appears relatively glossy and reflective. Only by 30 seconds does it gradually become matte. From the perspective of bloom mechanics, blooming allows the coffee grounds to release gases, promoting even extraction later. When the surface remains glossy, it indicates the coffee bed is still expanding or continuing to release gases. Only when the surface becomes matte does it prove that water has begun to seep downward, and the surface layer has reduced gas emissions, lacking sufficient support to maintain moisture on the surface. At this point, the bloom process can be considered properly complete.

The left side shows experimental group ①, the right side shows experimental group ②; visually, they are basically indistinguishable.

2. Comparative tasting after brewing:

The Yemen Mocha in group ① showed distinct nutty, chocolate, spice, and red berry flavors, with a slight tea-like finish and medium body.

The Yemen Mocha in group ② also presented rich nutty, chocolate, spice, and red berry flavors, with a slightly stronger aftertaste than group ① and a slightly fuller body.

From the tasting comparison above, we can conclude that the difference between a 20-second bloom and a 30-second bloom (that is, timing from the beginning of pouring versus timing after pouring completion) is not as significant as one might imagine.

Conclusion

Overall, as long as water temperature and grind are correct and the blooming technique is properly executed, slight variations in bloom time (within 10 seconds) don't have as significant an impact on the overall pour-over result as one might think. In fact, if the two cups weren't tasted side by side, you might not even notice the difference. The real purpose of this experiment isn't to encourage obsessing over 10 seconds of bloom time, but rather to encourage careful observation of the coffee bed surface during bloom to determine when blooming is complete. After all, different roast dates, water temperatures, and grind sizes all affect bloom effectiveness and duration. My recommendation of 30 seconds bloom time is only for coffee at peak flavor development, with allowance for a few seconds of variation.

If coffee beans have been rested for a considerable time (for example, a month or more), then the coffee grounds should be entering the final stages of degassing (meaning they barely expand and collapse quickly after water is added). In this case, don't feel bound by the 30-second bloom recommendation. As soon as you notice the coffee bed surface change from glossy to matte, you can immediately end the bloom and proceed to the next pouring stage.

After all, there are no absolute standards or definitions for blooming. In our process of learning pour-over techniques, when referring to videos or data, don't forget to observe whether bloom timing is calculated from the beginning of water addition or after completion, and adjust to your preferred bloom timing. In my observation, many expert baristas' brewing videos start timing bloom after pouring is complete, so I also recommend using this definition as the standard when sharing techniques. Some schools of thought start timing from the beginning of pouring; in those cases, simply subtract the pouring time to calculate the actual bloom duration.

Alright, that's all for this installment. If you still have questions about blooming, feel free to leave a message for the editor. If there are any omissions or inaccuracies, everyone is welcome to leave comments for supplementary discussion.

Looking forward to the next knowledge sharing! Let's work together to improve our professional skills!

Image source: FrontStreet Coffee

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473