Pouring hot water into the dripper makes the coffee grounds swell. Watching this process is also part of the enjoyment of hand-drip coffee.
This initial step of pouring hot water and waiting briefly is called "blooming."
What you want to see during blooming is not just whether the grounds swell significantly. It's also crucial to ensure that the hot water permeates all the grounds.
This article will focus on paper drip brewing and explain the meaning of blooming and practical guidelines you can try at home.
Why do bubbles appear when hot water is poured?
During roasting, gas is generated in coffee beans, with carbon dioxide making up most of it. Some remains inside the beans and is gradually released during storage.
When grinding or extracting the beans, this release accelerates. The bubbles and swelling observed when pouring the first hot water are related to this gas release. The relationship between gas release and extraction has been explored in research. [Smrke et al., 2018]
The degasification that occurs in the bag and the bubbles visible during extraction are not separate events but are connected as part of the changes in roasted beans.
During blooming, observe how the grounds are wetted.
When blooming at home, in addition to observing the gas release, try to check if any dry grounds remain.
If you only pour a small amount of hot water into the center and wait, dry areas may remain on the outer edges. Simply adhering to a set time won't ensure that all the grounds are wetted.
Pour the initial hot water aiming to cover the entire surface of the grounds. Instead of focusing on "creating a beautiful dome," observing where the water reaches will help you consistently brew each time.
Note that coffee components are extracted even at this stage. It's not that "nothing is extracted while waiting, and then extraction begins afterwards."
How long should the blooming time be, and how much water?
If your equipment has a recommended recipe, start there. For example, HARIO's W60 recipe suggests 50g of water for blooming 20g of grounds for 30 seconds. [HARIO "W60 Dripper"]
If there isn't a specific recipe, you can consider the following settings as a starting point for comparison at home:
| Item | Starting point for testing |
|---|---|
| Coffee grounds | 15g |
| Water for blooming | About 40-45g. Prioritize ensuring no dry areas remain. |
| Until next pour | 30 seconds from the start of the first pour. |
| Water measurement | Include the blooming water in the total recipe water amount. |
| Subsequent extraction | Continue with your usual recipe consistently. |
This is a suggested comparison from 0566 and not an optimal value for all beans. For example, if you decide on a total of 240g of water and pour 45g initially, 195g remains. Adding extra for blooming would change the beverage's concentration.
If the coffee doesn't swell, is it old?
When the grounds swell well, they appear fresh. However, freshness and quality cannot be determined solely by the amount of swelling.
Research has shown that the way gas is released varies depending on the roast level, roasting conditions, and the difference between whole beans and ground coffee. Therefore, comparing beans with different conditions based solely on swelling is not appropriate. [Smrke et al., 2018]
If you feel the swelling is small, check the roast date and storage conditions, as well as if the roast level is the same as previous beans. Ultimately, judge by aroma and taste.
Instead of constantly changing your brewing method to achieve larger swelling, finding the conditions that make the beans enjoyable to drink will lead to actual deliciousness.
Does longer blooming make it tastier?
It cannot be definitively said that extending blooming from 30 to 45 seconds will always make the coffee sweeter or more bitter. Changing the waiting time also alters the total extraction time and the temperature progression of the grounds.
If you want to know the difference, first try tasting coffee brewed with 30 seconds and 45 seconds of blooming. Keep the amount of beans, grind size, water temperature, total water amount, and subsequent pouring as consistent as possible.
It's difficult to make the same cup exactly multiple times, so there's no need to rush to a conclusion after just one comparison. Even noting impressions like "I prefer the aroma of this one" or "The aftertaste feels lighter" can be helpful for your next brew.
Some equipment skips blooming.
Blooming is not a process required in the same way for all brewing equipment.
HARIO also has coffee pots designed for a single pour without a separate blooming time. The method of wetting the grounds and proceeding with extraction varies depending on the equipment's structure and recipe. [HARIO "Coffee Pot for Beginners"]
There's no need to apply the procedure for your usual dripper directly to other equipment. First, determine the brewing method suitable for that specific equipment.
0566's recommended way to enjoy blooming
At 0566 Coffee Roasters, we consider the balance of acidity, sweetness, and aftertaste through roasting. When brewing these beans at home, the final thing to consider is whether the resulting cup tastes how you like it.
The blooming time in seconds serves as a guide to keep conditions consistent each time. Observing how the grounds are wetted and the state of the bubbles provides clues for understanding the beans.
Then, if it tastes delicious, remember the amount of beans, water, and blooming time. Before trying more advanced techniques, start by being able to re-brew your favorite cup.
References
-
Smrke et al. (2018) Time-resolved gravimetric method to assess degassing of roasted coffee
-
HARIO W60 Dripper
-
HARIO Coffee Pot for Beginners
