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The Importance of the Coffee Bloom

I spend a lot of time on this blog talking about the benefits of using coffee that is as fresh as possible. I urge you to buy your beans as soon after roasting as you can (or even better, roast your own) and to grind just before you brew.

I’ve shared reviews of beans and coffee equipment to help you get the best from your cup of Joe. Which is why it is now my duty to tell you about the drawback of truly fresh coffee:

Carbon Dioxide.

Not one to bring you a problem without a solution, read on to learn how to degas your fresh grounds for premium flavor. In other words: how to bloom coffee.

Coffee Bloom Explained

You may have come across the phrase, ‘coffee bloom’ during your research into the perfectly brewed cup. It’s most commonly used among devotees of pour over methods. It simply refers to pouring a small amount of water over your coffee, and allowing that to sit for a short while (usually about 30 seconds) before you continue brewing.

Coffee Blooming in a chemex

If you’ve ever seen coffee when it’s blooming, you will have noticed that the grounds swell, and bubbles rise to the surface of the liquid. Those bubbles are carbon dioxide (CO2) being released by the beans.

New to pour-over? Catch up by reading our beginner's guide before you go any further. Don’t worry, we’ll wait.

Carbon Dioxide

Here’s the coffee bloom science. CO2 is inside every coffee bean as it grows. From the moment the beans are roasted, the gas begins to escape. In fact, the darker your beans are roasted, the less CO2 you can expect to find in them.

When beans are ground the surface area increases, and they degas far more quickly than whole beans. The problem with this natural degassing is that the volatile compounds that give coffee its flavor escape with the carbon dioxide, making the coffee go stale.

CO2 is our friend, right until the point where we come to brew. There are two ways in which the gas negatively impacts the flavor of your drink:

  1. Carbon Dioxide tastes sour. While that’s refreshing in a glass of carbonated water, it isn’t a flavor profile that we want from our premium beans.

  2. The gas stops water from coming in contact with the coffee. Until the gas has released, the water cannot do its job of extracting all the delicious compounds necessary for your brew.

For those reasons, it’s worth adding another 30 seconds to your brewing time, in order to release the gas.

How to Bloom Coffee

step by step guide to bloom coffee

There’s nothing complicated about getting your coffee to release the gas:

  • Put your freshly ground beans into your favorite pour over coffee maker.
  • When your water is at the right temperature, measure out twice as much water (so for 25g of beans, 50g of water).
  • Pour the water over the coffee.
  • Wait 30 seconds. You should see the coffee puff up, and bubbles of gas release from the surface.
  • Pour the remainder of your water and brew as normal.
PRO TIP: To get a really controlled pour, consider getting a gooseneck coffee kettle

Watch this video for a full demonstration of blooming from Coffee Lovers TV.

There are a number of factors that affect how much gas is released when you bloom.

  • I’ve already mentioned the freshness of the coffee.
  • Roasting also releases CO2, so the darker you like your roast, the less bubbling you will see when you bloom.
  • The bean hardness can also make it more difficult for the carbon dioxide to make its way through the bean.
  • Other things can affect the process too, like the temperature of the water, and the heat and humidity on the day you brew (colder temperatures mean less gas release).

In general, though, seeing a lot of bubbles means that you are working with really fresh coffee.

Tips for blooming with different brewing methods 

While the pour over method is by far the option that benefits the most from blooming, it doesn’t hurt to bloom before you brew regardless of your preferred technique.

Here are a few tips on how to bloom with some of the more popular brewing methods out there. Find the one you use and try blooming a batch to see if you can taste any improvement!

Pour Over

Here we have the tried and true “bloom champion”.

If someone is casually talking about blooming coffee, chances are they’re talking about a pour over like the Hario V60 or the Chemex.

Chemex coffee on the table

However, don’t assume that because you’re blooming with your pour over, it means nothing else will matter anymore. You’re still going to want that perfect grind for your Chemex and to start with fresh beans at the right grind (medium-coarse) and ratio (55 grams per liter). You can then dial your brew in till it's just the way you like it.

Otherwise, you should be able to employ the same method as in the instructions above.

French Press

This is another wildly popular yet incredibly simple brewing method. Not only is it easy to use, but it also can benefit from a “blooming” stage in the brewing process as well.

NOTE: If you’re interested in finding out all of the nitty-gritty details on brewing with a French press, feel free to check out our step by step guide here!

When it comes to blooming with a French press, you simply need to insert the “bloom time” right into the process where it would naturally go.

French press coffee brewing

Once you’ve ground the coffee and added it to the carafe, add the appropriate amount of water (following the above instructions) right into the carafe along with the grounds.
Give them thirty seconds to bloom, stir them gently, and then add the rest of your water!

PRO TIP: Remember, that 30 seconds of blooming is counted separately from your brew time, which should be around 3-4 minutes.

Automatic Drip Makers

Now, chances are you use the drip maker for the convenience of it all, so it’s going to be bothersome to add an extra step into your brewing routine, but trust us, this really is worth trying at least once to see if you’re getting the best extraction possible!

When it comes to drip makers, all you need to do is boil a small amount of water before starting the coffee maker. When you’re ready to brew – and the separately boiled water is hot – add your filter and coffee grounds to the basket and pour an appropriate amount of water onto the grounds based off the above instructions.

PRO TIP: Make sure that your carafe is under the grounds when you do this to catch any water that gets through!

In this case, it’s typically suggested that you give the grounds 45-90 seconds to bloom (1).

When done correctly, you may find that after brewing, there isn’t that normal sinking spot in the center of the grounds where the water was hitting. This is because once properly bloomed, the water may tend to rest on top of the grounds and then work its way through them more evenly, allowing for a better extraction in the process.

Drip coffee maker

If you’re a drip coffee maker user and you’re rolling your eyes at these “extra steps” to your coffee brewing routine, we hear you, and the truth is, often drip coffee doesn’t benefit as radically from blooming as pour over. But if you decide the difference really is too much to pass up, there is another option available to you besides adding hot water beforehand.

There are specialty higher-end drip brewers available that actually come with a bloom function.

Cold Brew

While there are many ways to brew cold brew coffee (and many ways to drink it, as well!), if you’re interested in experimenting with blooming your cold brew coffee, you may want to consider trying the “hot bloom / cold brew” method (2). This involves utilizing some of the best benefits of both methods in one unified brewing experience that really does deliver some incredible java.

cold brew in a pitcher

In short, the method involves adding your coarsely ground coffee into the container and, once again, adding an appropriate amount of hot water based on the above instructions directly onto the grounds for 30-45 seconds.

From there, you add the rest of the cold water and let the concoction brew for the typical 12-24 hour period that cold brew requires.

Manual Espresso Machine

Yes, your manual espresso machine will benefit from the bloom, though it doesn't look like the bloom in a Hario or even a French press. It isn't even called a bloom, but it serves at least part of the same purpose: to fully wet the coffee grounds to help with extraction and ensure best flavor.

In espresso machines, this is called pre-infusion. In addition to wetting the coffee grounds, pre-infusion also helps the coffee swell up inside the portafilter, which increases the resistance to pressing the hot water through the filter basket. This ensures maximum surface contact with the hot water, which results in a richer flavor in the espresso produced this way.

lever espresso machine pulling a shot

How do you bloom - okay, pre-infuse - with a lever espresso machine? Simple: Lift the lever till it "latches" into position, wait 15 seconds to let the filter basket fill with hot water, and then do a 15-second pull just to halfway on the lever's travel. A small amount of espresso will trickle through. (At least, that's the technique with the La Pavoni in the Homegrounds Test Kitchen.) You'll note that letting the filter basket fill and then doing the half-pull works out to 30 seconds - the same time as a pour over bloom. Then, lift the lever again and do a full 30-second pull. 

Espresso preinfusion is similar to prewetting during a hand pour or batch brew. Ideally, espresso preinfusion occurs at a zero bars of pressure and a low flow rate (say, 2--3 ml/second), and pressure does not increase until the entire coffee bed is wet -Scott Rao

Many high-end automatic espresso machines have a pre-infusion stage built into the brew cycle; in this case, all you do is push the button and the machine does the rest. In either case, it's an important part of getting the best crema and the most intense espresso flavor, whether for a straight shot or for use in a cappuccino or latte.

When is Blooming Necessary?

As I already mentioned, adding a bloom into any brewing method won’t have a negative impact. Immersion methods, or more intense methods like percolators or espresso machines, just don’t benefit as much as pour over.

The reason for this is that pour over methods put the water in contact with the beans for the shortest length of time. If you have something (read: CO2) stopping the water from extracting flavor, it’s going to show up in the taste.

On the other hand, while using something like a French press can still benefit from blooming, the grounds are going to be in contact with the water for quite a bit longer, so you don’t have to worry quite as much.

The only exception to that is cold brew. Because the hot water is such a help in removing the gas, it can be useful to use that hot bloom/cold brew recipe. Bloom your coffee with hot water before you go on to cold brew it, to ensure real clarity of flavor.

Some coffee gurus make pouring water over coffee look like an art form. Watch this video to see how:

While you don’t need to make your brew quite that much of a ritual, you do want to make sure that the water is spread evenly through the grounds. This will help to get an even release of gas through the beans.

As we mentioned before, a gooseneck kettle will help with the pour.


Nirvana

Do you see what I did there? Nirvana played ‘In Bloom’ and it’s another word for heaven.

Coffee heaven?

No. Never mind. The key to a purer coffee flavor could just be another 30 seconds to your brewing routine. Give it a try the next time you’re pouring-over, and let us know if you can taste the difference.

Leave us a comment below if you’re a die-hard bloomer, or share your experiences with gassy coffee. We’d love to hear from you.

Frequently Asked Questions

Do I count the grams of water in my bloom as part of the total weight?

Yes, count the grams of water in your bloom as part of the total weight. For example: using a 600-ml Hario V60 brew using 33g of coffee (following the SCAA "Golden Ratio" of 55g/liter), you would pour 66g of water for the bloom - twice the weight of the coffee. If you follow the normal procedure for the Hario, adding approximately 200g of water every 30 seconds, you should stop at 600g total weight. Note that if you tare your scale after the 66g bloom and then add a full 600g later, you will have a 10% difference in your water-to-coffee ratio. The true answer? Do it both ways, then decide which one tastes best to you. Your mouth is the final judge.

Can I skip the bloom on a French press?

Whether or not you can skip the bloom on a French press is a slightly controversial question. Some experts claim that with immersion brewing, it's more important to keep the brewing temperature consistent by pouring all the water at once, and then stirring to ensure proper contact with all the beans. They claim that the CO2 will degas into the liquid and rise to the surface - and as any French press lover knows, there's a layer of foam (looking a lot like a bloom) on the top of the brew when it's time to press the plunger. Our advice: try it both ways and see which tastes best to you. We've found that the additional bloom time is trivial, and helps distribute the primary pour more evenly. 

Why doesn't my coffee bloom?

If your coffee doesn't bloom, the most likely issue is that the beans are not as fresh as they should be. While some coffee enthusiasts observe that dark roasted beans do not show as large a bloom as light or medium roasts, you should still see a swelling and "cap" of coffee grounds with a dark roast, if it's fresh enough. 


References

  1. Quinn, M., Lane, D., Zyni, Adam, Mike, Mark, F., . . . Sidhu, A. (2018, December 09). What is Coffee Bloom? Retrieved June 1, 2019, from https://foodal.com/drinks-2/coffee/guides-coffee/what-is-bloom/
  2. The Only Cold Brew and Iced Coffee Guide You'll Ever Need. (2018, May 30). Retrieved June 1, 2019, from https://blog.mistobox.com/blog/2018/05/28/the-only-cold-brew-and-iced-coffee-guide-youll-ever-need/
  • Alex
  • February 13, 2018
Alex
 

Alex is the Founder and Editor of Homegrounds.co. He is passionate about brewing amazing coffee at home, and teaching others to do the same.

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