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What Exactly is a Coffee Bloom?

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It doesn’t matter if you have the best coffee maker you can get your hands on if you lack some of the basic coffee brewing fundamentals you’ll still struggle to get a good tasting cup on par with your local coffee house.

​Like everything knowledge is the key, the more you learn regarding brewing coffee at home the better you’ll be. If you’re not ready to put in a bit of legwork and spruce up your coffee brewing technique maybe you’d be better off going back to instant coffee.

​Looks like a few of you reading this have run off back to your Nescafé instant, but for those of you still sticking around, I’ll be talking about the coffee bloom in this article.

​The “coffee bloom” is one of the key variables that can transform your coffee from a mucky sour brew to a perfect tasting cup good enough to impress any bearded hipster barista.

​What is a Coffee Bloom?

The coffee bloom is a natural part of any brewing process, and the “bloom” starts when the hot water hits the grounds causing CO2 gases to become released (If your coffee is fresh, it’s releasing CO2 which repels water). As you introduce a small amount of water (just enough to get your coffee wet) to your coffee grounds the CO2 is expelled out of the cells of the coffee, which by the way contain all those oils and aromatics, the fresher your coffee, the bigger the bloom!

​The coffee bloom typically lasts for 30 seconds, and you should see your coffee grounds start to bubble and expand into a dome-like shape, at this stage you can continue with your pour. Giving your coffee 30 seconds to bloom will enhance its flavors (depending on how recently it was roasted).

…Still with me? Good.

​So basically the coffee bloom allows the water to displace most of the CO2 which then 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 and most of the degassing (releasing of CO2) has already occurred and unfortunately along with that most of the flavor compounds within the beans will have also deteriorated.

​The coffee bloom happens in every non-espresso extraction and other brew methods that use fresh coffee.

​5 Variables That Can Affect the Bloom

The coffee bloom doesn’t “just happen” many variables can play a role in the releasing of CO2, and in turn, can have an adverse impact on your bloom. I have listed below a few of the factors that can influence the rate at which the CO2 can be lost the moment the coffee beans leave the coffee roaster, let’s take a closer look.

​1. Storage Temperatures

​If you store your whole coffee beans in a hot place, expect the coffee beans to lose CO2 rather quickly (not good). I recommend storing your whole coffee beans in an airtight container in a cool, dry place and away from direct sunlight; at the back of a kitchen cupboard is a great place (as long as it’s not over your hot stovetop!).

​Learn how to correctly store coffee beans – remember: Heat means more gas release and you want to avoid this.

​2. Humidity and Coffee Beans Don’t Mix

​Just like heat, dry, humid storage conditions will allow for more CO2 to escape. Not only that, but humid environments can also encourage fungus and mold to grow on your coffee beans (NOT good!).

​3. Different Roast Levels

​Different coffee roasts will have varying blooms. For example, dark roasts (such as those Italian roasts) will contain less CO2 when compared to the same coffee roasted at the Full City level.

​So your roast level will affect how much gas will be released during the bloom stage, make sense?

​4. Where The Beans Come From

The origin of the whole coffee beans (where they were grown) can also impact the bloom. Some coffee growing regions are known to have more out-gassing than in other regions.

​5. How Hard Are Your Beans?

​The harder the coffee beans are, the more difficult it will be for CO2 gases to escape and make it through the coffee bean.

​To Bloom or Not to Bloom?

​Yes, you most certainly want to bloom your coffee if possible. By adding in just enough water to moisten the freshly ground coffee (rule of thumb: 2 grams of water to 1 gram of coffee – read more on coffee ratios) will allow for the CO2 to escape which will vastly improve the taste of your cup and it will show you just how fresh your coffee beans actually are.

​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 such as the Chemex, and Automatic Drip Brewers (yes you can bloom coffee in those too).

coffee blooming stages

How to Bloom Coffee?

​As I’ve already covered to bloom coffee involves pouring just water over freshly ground coffee beans to allow for the gases to escape.

However, the process does vary slightly depending on what type of coffee brewer you are using. Let’s take a look at the familiar three coffee makers.

​How to Coffee Bloom with a French Press

If you are not sure of the brewing basics, make sure you check out my article how to use a French Press, before you get ahead of yourself and start worrying about the coffee bloom when you haven’t mastered the basics.

​If you already know how to use a French Press, simply pour you water over your coarsely ground coffee beans. Remember to pour just enough water to soak the coffee grounds, think of a wet sand consistency, or about 2-parts water to 1-part coffee.

Depending on just how fresh your coffee is you should start to notice a bubbling bloom forming on top of the water. Stand back and let the bloom remain for 15-20 seconds. While waiting, you can admire the awesomeness and take in the smells, once done slowly stir the coffee bloom. Stirring will ensure that all of the coffee grounds become fully saturated with water.

​Once stirred continue with the pour and your usual French Press routine, depending on how strong you like your coffee leave the French Press steeping for up to 4 or 5-minutes.

Pour Overs and Coffee Blooms

The coffee bloom process is slightly different when using a Chemex pour-over, or any pour-over method for that matter. To start the blooming process, slowly pour your hot water (not boiling water) over your freshly ground coffee beans, in a circular motion starting from the outside and then slowly working your way into the middle.

​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 that coffee starts to drip through the filter. Let the coffee bloom for roughly 60-seconds if you are using a Chemex. Once the bloom has finished, continue with the pour and your regular “pour over” routine.

Coffee Bloom Using Automatic Drip Coffee Makers (Yes it’s possible)

​If you are still using an automatic push-button drip coffee maker, you obviously haven’t spent too much time on the Bean Ground coffee blog reading through our articles, so you’ve yet to venture into the real world of manual coffee brewing.

​Hey, that’s okay, but I strongly suggest that you ditch those push-button coffee makers and find out what you’re missing with manual brewing.

​To coffee bloom using a drip coffee maker first begin by placing a filter into your basket (I would recommend using a Gold Tone filter). Next, add your freshly ground coffee beans and then pour in just enough water to soak the grounds, just like the Chemex you want to saturate the coffee but not too much, you don’t want the water to start dripping through the filter.

​You should now start to see the bubbling coffee bloom at this stage, wait for a minute to a minute and a half, then just operate the auto-drip coffee maker as you normally would.

​If you bloom your coffee before your regular brewing cycle, you’ll notice that the water will form an even pool on top of the coffee grounds rather than the few drip depressions. This even pool of water will allow for an evener extraction and an ultimately better-tasting cup.

Mark Morphew

Mark is the Editor-in-Chief of the popular coffee blog - Bean Ground. He's been active in the catering and hospitality industry for over 20 years. When he's not fiddling around with a new coffee gadget, you'll find him busy working on his other passion, web development. You can discover more about Mark here.