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What Is A Coffee Bloom? Why Does It Matter?

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Are you struggling to brew a cup of coffee at home that tastes as great as a cup from your local coffee shop? You might think you’ve covered everything, ticked every box, and got yourself the best gear you can afford, but have taken a look at your coffee bloom.

Coffee blooming is a crucial variable often overlooked by many home coffee enthusiasts in the early learning stages.

However, this process shouldn’t be overlooked. Once you understand the benefits of blooming your coffee, you’ll bring life into your once dull and sour brew, turning it into a perfect tasting cup that will impress almost any loyal coffee aficionado.

What Causes A Coffee Bloom?

I’m sure you’ve heard baristas at your local coffee shop mention the “bloom” when they’re talking with colleagues behind the counter, and you probably found yourself momentarily confused.

After all, it’s a strange term to use when brewing coffee, and it’s something you would expect to hear in a florist rather than at Starbucks!

coffee bloom bean ground

What is a coffee bloom? You’ve probably seen this reaction before when your coffee grounds start to swell and bubble up but had not released that it had a name and a reason behind it.

The coffee bloom is a natural part of any brewing process, and the “bloom” starts when the hot water hits the grounds causing gases to be instantly released.

As you introduce a small amount of water to your coffee grounds, CO2 is expelled from the cells of the coffee; the fresher your coffee, the bigger the bloom!

​The coffee bloom typically lasts for 30 seconds, and you will see your coffee grounds start to bubble and expand into a dome-like shape; at this stage, you can continue with your pour.

Simply put. The coffee bloom allows the hot water to displace most of the CO2, which essentially preps the coffee bed for proper extraction.

If you don’t see a coffee bloom, it most likely means that your coffee isn’t fresh. Most of the degassing (releasing of CO2) has already occurred, and unfortunately, along with most of the flavor compounds locked within the beans, will have also deteriorated.

So blooming coffee is a good thing to do, and it tells you a lot about the quality of the coffee beans.

The Grind And The Roast Matters

The key to a terrific coffee bloom experience paired with a rich and flavorful brew is to keep the freshly roasted coffee whole for as long as possible.

This means only buy whole roasted coffee beans, ideally within one week of the roast date, and grind just before needed.

Once the coffee has been ground, there is more surface area. This will cause the gas to release quicker; the coffee no longer has a protective shell keeping the gas locked inside.

kalita wave wth ground coffee bean ground

The science behind coffee blooming is fascinating, and understanding how carbon dioxide interacts with your coffee is something worth learning.

 – Let’s take a closer look.

Carbon dioxide has a sour taste. So when your coffee doesn’t bloom due to old stale coffee, or you haven’t left enough time for the blooming to degas, the CO2 will infuse your coffee, giving it a sour taste.

Carbon dioxide also repels water, which isn’t a good thing when you’re trying to wet your ground coffee and will cause under extraction.

It’s the water that extracts the aromatics and flavors from the coffee, so if the carbon dioxide hasn’t had a chance to disperse, the water won’t fully interact with the coffee.

But remember, carbon dioxide has a sour taste. So if you haven’t bloomed your coffee, you will have a sour taste and a limited extraction, which equals bad tasting coffee.

Factors That Affect How Coffee Blooms

Blooming coffee isn’t always a given. As I’ve already mentioned, the freshness of your whole bean coffee is a crucial variable, but many other factors can affect the bloom.

The following are known to impact the rate at which the gas is lost from the coffee beans as soon as they’ve completed the roasting process.

Coffee Bean Origin

The origin of the coffee bean can impact coffee bloom time. Some regions produce coffee that will degas faster than other coffees grown in other areas.

Coffee Roast level

Different coffee roasts will have varying blooms. For example, Darker Italian roasts typically contain less gas compared to lighter roasted coffee.

Temperature And Storage

Proper coffee storage is vital to not only an impressive bloom but also to the overall freshness of your coffee.

Storing coffee in a hot environment will allow the gas to escape faster. We recommend that you keep your beans stored inside of an opaque container at the back of a cool pantry or cupboard.

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Humidity

Humidity and correct storage go hand in hand.

If you invest in a good coffee canister and keep your coffee away from anything that generates heat in your kitchen, such as your kettle or stove, you shouldn’t have anything to worry about.

Grind Size

And last but not least, the size of your ground coffee.

Even something as simple as how fine you’ve ground your coffee will affect just how quickly it will release carbon dioxide.

Fine grinds will release gas from the surface area far quicker than coarse ground coffee because there is more surface area for the carbon dioxide molecules to condense and stabilize.

To Bloom Or Not To Bloom?

I’m sure if you’ve gotten this far, you will already know the benefits of blooming your coffee.

The brewing method is pretty straightforward and involves adding just enough water to moisten your freshly ground coffee (rule of thumb: 2 grams of water to 1 gram of coffee – read more on coffee ratios).

​Depending on your coffee maker, the coffee bloom process will be slightly different.

So keep on reading, and I’ll briefly cover how to bloom coffee in a French Press, pour overs like the Chemex and Automatic Drip Brewers.

How To Bloom Coffee

The blooming process does vary slightly depending on what type of coffee brewing method you are using.

Let’s take a look at the familiar three coffee makers.

Pour Overs

For pour-over coffee with brewers like the Hario V60 or the Chemex, slowly pour hot water in a circular motion starting at the outer edge, being careful not to hit the paper filter, and slowly working your way to the center.

The trick is to use just enough water so that the coffee grounds are saturated and uniformly soaked, but they don’t become too wet so that coffee starts to drip through the filter.

Let the coffee bloom for roughly 60-seconds. Once the bloom has finished, continue slowing pouring water using your gooseneck kettle and regular “pour over” technique.

French Press

For the French Press, the blooming process is very similar.

Once you have added your coarse ground coffee to the French Press, slowly pour a small amount of hot water over the grounds.

You need to add just enough water to dampen the coffee – try to aim for a wet sand consistency or about 2-parts water to 1-part coffee.

If your coffee is fresh, you will immediately start to see the coffee grounds bloom.

Let the process play out for about 20 seconds and gently coax and stir the grounds to make sure that they all contact the water.

Once you’re satisfied, complete your regular French Press brew regime.

Automatic Drip Coffee Makers

Yes, it’s also possible to bloom coffee using a push-button automatic drip coffee maker.

Place your paper filter into the drip basket (get better results using a Gold Filter like this) and add your ground coffee.

Slowly pour in just enough water to soak the grounds but not too much that it will penetrate all the way through and drip through the filter into the carafe.

Allow the coffee to bloom for roughly 60 seconds and continue with your regular brew cycle on your machine.

When you let the coffee bloom in an auto-drip brewer, you can definitely taste the difference compared to not blooming.

Pre-infusion of water will form an even pool on top of the coffee grounds rather than the few drip depressions created by the machine.

This even pool of water will allow for an evener extraction and an ultimately better-tasting cup.

FAQs

📌 Can You Bloom Coffee With An Espresso Machine?

Absolutely, yes, you can bloom with an espresso machine – it’s called pre-infusion.

With most top-end espresso machines, the brew cycle will pre-infuse and saturate the grounds at low pressure and flow before ramping up to full pressure and flow.

📌 Do You Bloom Pre Ground Coffee?

No. Even if you try, it’s going to be very difficult to bloom pre-ground coffee.

The reason being, the coffee needs to be fresh to actually bloom.

Whole bean coffee will trap all of the natural gases inside. But as soon as you grind the coffee, the clock starts ticking, and the carbon dioxide starts to disperse – no CO2 means no bloom.

📌 What Happens If You Don’t Bloom Coffee?

If you’re brewing fresh coffee, we highly recommend a 30-second minimum coffee bloom time.

The blooming process enables the trapped carbon dioxide within the structure of the coffee beans to be displaced by the water.

If you do not allow the coffee to bloom, the carbon dioxide gas will prevent the complete saturation of the grounds – the CO2 will repel the water, resulting in thinner brews with less flavor.

📌 Do Storage Conditions Impact Bloom?

Yes. Whole bean coffee should be stored in an airtight, opaque container away from heat, light, and moisture.
If the freshly roasted coffee has been stored at a hot temperature, more gas will be released – less gas means less flavorful brewed coffee and no bloom.

Mark Morphew

Mark is the editor and writer of the popular coffee blog Bean Ground. He's been active in the catering and hospitality industry for many years. When he's not fiddling around with a new coffee gadget, you'll find him busy doing DIY projects around the home and taking his German Shepherd for a walk, who funnily enough is called Kona! You can discover more about Mark here.