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 flavour. 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.

Related: What is Pour Over Coffee? Is It Good?

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 flavour 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 flavour of your drink:

1. Carbon Dioxide tastes sour. While that’s refreshing in a glass of carbonated water, it isn’t a flavour 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.

Yes, coffee is degassed after roasting, but you’ll need to finish off the process as your brew. Here’s how:

How To Bloom Coffee

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

• Put your freshly ground beans into your favourite 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.

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.

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 litre). 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.

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.

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!

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.

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 centre 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.

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.

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 the best flavour.

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 flavour in the espresso produced this way.

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. 

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 flavour, 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.

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 flavour.

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 flavour 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.