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What is coffee bloom?
Coffee bloom is mandatory for hardcore pour-over enthusiasts. But does it make any difference?
Published February 22, 2022
Yker Valerio
Coffee experts@The Coffee Lab
Coffee bloom is essential for pour-over coffee. In theory, pre-infusing the coffee grounds before pouring all the water releases the residual CO2 and prepares the particles to obtain a more even and thorough extraction.
All coffee brewing masters and hardcore aficionados agree on the importance of the coffee bloom. But, as you may know, the coffee community is a fertile ground for pseudo-science and superstitious myths. For years, people believed that oily coffee beans are better, coffee should be black as your soul, or dark roasts have more caffeine than light roasts.
So, is coffee bloom just another of these myths? Or does it add up to the coffee brewing results?
Come with me to find out!
What is blooming?
Blooming is a preliminary step to prepare the coffee bed for a pour-over. After pre-wetting the filter and shaking the dripper to level the grounds, the next step in any pour-over routine is the coffee bloom.
It is to wet the coffee bed with a small amount of water so that the grounds release residual CO2, and improve extraction, making it more uniform.
During the blooming process, bubbles burst from the coffee bed for several seconds. The reason? Theoretically, pouring all the water in a single flow from the start would produce a different result. The gas coming from the coffee grounds disturbs extraction, moving the coffee grounds and sabotaging the otherwise uniform flow.
In short, blooming is to wet the coffee bed to obtain a more uniform extraction during the pour-over coffee brewing by reducing and controlling turbulence.
For this reason, most experts recommend using a specific ratio of water to dry coffee for the bloom. While 2:1 has become widespread, some professionals propose to use 3:1 and even 4:1.
In my experience, 2:1 can be challenging, as you’ll need a steady hand and a good gooseneck kettle to wet the entire coffee bed.
What makes coffee bloom?
Pour-over coffee lovers swear by the beauty of the coffee bloom. And it isn’t only because we are extremely sensitive and poetic. A good bloom reveals one of the most exciting aspects of high-quality coffee: freshness.
Suppose you have the opportunity to test this claim. In that case, you’ll be surprised by the difference between stale coffee, regular coffee, and fresh coffee.
Fresh coffee produces more bubbles during blooming than regular coffee, and stale coffee won’t make any bubbles. For this reason alone, the coffee bloom has become essential for the pour-over coffee brewing ritual. It’s like learning in the first few seconds if the coffee grounds are worthy or not!
Grinding coffee just before brewing makes a difference here, but it doesn’t make all the difference. You’ll notice a more vibrant bloom when coffee is freshly ground than when it comes already ground from the bag.
Anything between one and four weeks is ideal. It varies depending on the roast type and storage, but it’s a decent range to aim for. Sometimes freshly ground coffee won’t produce any bubbles because of the roasting date. In contrast, only well packaged whole beans would offer most of their aromatic profile after one month and up to three months after the roasting date.
On the other hand, ground coffee is hopeless after a week, even when properly stored. Here, some coffee enthusiasts freeze ground coffee to preserve freshness. Still, there is a high risk of undesirable odors coming into the coffee grounds in most home freezers.
Considering the price and convenience of a separate freezer for coffee compared to a coffee grinder, I would certainly recommend the latter.
Why is coffee bloom important?
Pour-over coffee brewing is a challenging craft. Obtaining a uniform and repeatable extraction by hand is difficult without the appropriate knowledge and tools. Yet, coffee blooming enhances extraction by provoking bubbles at the start of the brewing process. In doing so, the coffee bloom releases CO2 from the grounds initially, preventing the bubbles from disrupting extraction later.
As you may know, coffee extraction depends on several factors, including water temperature, brew ratio, time of contact, grind size, and turbulence. In this regard, coffee bloom reduces and controls turbulence during extraction. In doing so, the coffee bloom helps to get a smoother and more balanced extraction process.
If you have the chance, try an experiment and brew two pour-overs, one with a blooming phase and the other without it, and you’ll be able to notice the difference. A coffee bloom tends to produce a cleaner cup with less undesirable bitterness and sourness.
How to bloom coffee
As I said before, blooming coffee only makes sense for pour-over coffee. Although some people like to bloom their Aeropress brews, several tests suggest it’s pointless, just like in any immersion method like the French press and the siphon.
Factors that influence blooming and extraction
Bear in mind that coffee extraction changes considerably depending on crucial factors like grind size and dripper design. For instance, flat and conical pour-over devices have different drawdown times, with all other critical factors remaining equal.
Flat bottom drippers -i.e., Kalita Wave, Blue Bottle Coffee Dripper, Fellow Stagg- tend to create a slower flow, getting a bolder cup of coffee. On the contrary, conical drippers with a wide bottom -Origami, V60- create little resistance producing a cleaner and more delicate cup.
On the other hand, the finer the grind size, the slower the extraction is, and the stronger the result. Similarly, the brew ratio plays a massive role in coffee extraction and blooming. It’s considerably easier to bloom a generous dose of coffee grounds -around 20 g- than a smaller dose.
However, using a massive batch of coffee can be hard to handle. In my case, brewing a pour-over with more than 60 g goes beyond my skill level. For this reason, I recommend starting with 20 g and then increasing the coffee dose as you feel more comfortable.
Another factor is water temperature. Most people choose hot water to bloom coffee grounds, but as you might expect, some rebels have tried with cold water too. The latter is the case of Vincent from Tales Coffee Roasters, already trying something he calls a cold bloom.
Steps to bloom coffee
To add a blooming phase to your pour-over brewing routine, you’ll find a digital scale pretty useful. Some scales come with a timer, but if yours don’t have one, any timer works just fine -i.e., Smartphone, tablet, the online timer on the PC, etc.
- Measure your coffee beans and grind them.
- Put the filter on the dripper and rinse with hot water. Transfer this water and save it for later use -it’ll taste a bit cardboardy, but you can drink it alone safely or water your plants. In any case, avoid ditching water carelessly.
- Put the coffee grounds in the filter and shake the dripper a bit to level the coffee bed.
- Pour a small amount of water over the coffee. This is appropriately the blooming phase, so it takes twice the amount of coffee grounds in terms of water. That is a 2:1 ratio. So, for instance, if you’re brewing with 20 g of coffee, bloom with 40 g of water. To bloom accurately, tare your scale before adding the coffee grounds. Once you check the appropriate amount, tare the scale again and add the corresponding amount of water.
- There are at least two alternatives to wet all the coffee grounds evenly. The first is the Rao Spin, which is pretty popular and forgiving. It consists of holding the dripper and spinning it gently to move the water and the coffee grounds together, assuring that all the coffee gets wet. The second alternative is stirring in an NSEW motion. It consists of a stick to stir the grounds in four directions. It has the same purpose as spinning, to wet the coffee bed entirely with a minimum amount of water.
- After adding some turbulence with your favorite technique, the rest of the blooming process is just waiting. Although recommended times may vary, start with 30 seconds while checking if the water has drained fully or not. It serves no purpose to wait if there’s no water in the dripper.
- Here the bloom has finished already, and the next step is to pour the remaining water into your brewing recipe. Depending on the technique, you might pour all the water at once or in different phases, like the famous Tetsuo Kasuya 4:6 brewing method.
Coffee Bloom and Brewing Methods: Some considerations
A few extra considerations about coffee bloom and brewing methods here: it’s worth noting that immersion methods don’t get many benefits from blooming. Although there is a range of recommended bloom ratios, I chose 2:1 because using excessive water increases the chance of clogging.
Another aspect to consider is the degree of turbulence you may add when using the Rao spin or stirring.
As forgiving as both can be, performing any of both too aggressively increases extraction. If you aim for repeatability, I suggest controlling and simplifying each step in your brewing routine. It’s a bit of a nightmare to get a perfect brew without learning to get it again.
Final thoughts
If you haven’t started blooming your coffee for pour-over, now you found a good reason to do so.
Remember to experiment with bloom ratios to find the most suitable for your pour-over method. In any case, there is nothing here cast on stone.
So, give it a try and let us know how you liked it. Did you notice the difference?
About the author
Yker Valerio
Yker Valerio (he/him) is a freelance content creator. After more than 10 years of working as a management consultant, he started his blog Bon Vivant Caffè to share his passion for specialty coffee.
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