What Is Coffee Bloom And Why Is It Important?

I remember when I first heard of the term ‘coffee blooming’ I initially discarded it as something far too technical to be of importance to my coffee brewing routine. As I ordered a pour-over in my local coffee shop I watched in disbelief as the Barista, equipped with his ultra-fancy gooseneck kettle, proceeded to expertly pour a tedious volume of water over the coffee grounds, only to stand back dramatically and declare that it’s time for the coffee to ‘bloom’.

As far as I could tell, all he had done was dribble a tiny amount of water over the grounds and I was getting impatient. I wanted my delicious pour-over coffee and I was not keen to sit here and look at damp coffee grounds all afternoon.

Finally, the barista poured the rest of the liquid over the coffee and this delicious infusion eventually made its way into my coffee cup. I have to admit, it was a really great tasting mug of java and as I sipped away I started to consider this ‘bloom’ may be more important than I had first realized.

After having a long chat with this coffee expert, I found out that the coffee bloom is a process of de-gassing, so it releases carbon dioxide from the coffee. This results in a sweeter, less acidic brew but there are loads of factors that affect the bloom process. There are certain times, temperatures, and techniques to optimize your bloom depending on the brew method used.

As there was almost too much to take in, I decided to condense my new-found coffee wisdom and do an article dedicated to this important coffee blooming process.

What Is Coffee Bloom And Why Is It Important

What Do People Mean When They Say Coffee Bloom

Coffee blooming is the process where the ground coffee is exposed to just enough water to dampen it before the coffee brewing process begins. The barista will gently pour the correct amount of water over the ground coffee beans in a circular motion, just enough to allow them to expand and this starts the degassing process. It’s an essential step in most coffee brewing processes and not one that should be skipped to save time.

What Is Actually Happening To The Coffee

When the fresh coffee is sent to the roasters, the heat that is generated in the roasting process causes gasses like carbon dioxide to become embedded in the roasted coffee.

The coffee will degas naturally as time passes but this happens very slowly. Grinding up the coffee increases the surface area of it and will speed up the release of gas. Where the blooming process comes into this is due to the hot water that is poured over the coffee. This is absorbed by it and this stimulates a huge release of carbon dioxide.

The de-gassing stage of blooming causes the coffee grounds to bounce around and repel each other which creates a turbulent environment. This needs a bit of time to settle down before the rest of the water is added to ensure an even coffee extraction.

Coffee Blooming In A Chemex

Is The Coffee Bloom Good Or Bad

The more gas the coffee contains, the more variety of flavors it will release into the cup of coffee. Fresh roasted coffee is more flavorful thanks to the increase in gasses. This explains why it is important to store coffee in an airtight container to avoid excessive loss of gasses and why you should grind the beans just before you use them. The blooming process is important for great-tasting coffee so is definitely a good thing.

Why Allow Coffee To Bloom

Carbon dioxide dissolved in water creates an acidic environment and too much acid in your coffee gives it a sour taste and can be harsh on your stomach. If you immediately pour the full amount of water over the coffee then all this gas will remain trapped in the liquid. Allowing a large amount of the gas to be released before you submerge the coffee lessens the acidity and allows sweeter flavors to dominate the java rather than bitter and sour.

Factors That Affect Bloom

Humidity Levels

When you store your coffee the gas is always looking for a means to escape. If the coffee is stored in a very dry environment, then the gas will be able to escape easier compared to a moist area. Unfortunately, too moist an environment will lead to mold growth so you have to get the balance just right.

Roast Level

Darker roasts of coffee like Italian roasts trap more gasses compared to lighter ones. This gives them the more intense flavors and they can hold the gasses better over time.

Coffee Beans

Some varieties of coffee beans are just more prone to de-gassing compared to others. This varies from region to region as well as with the type of bean and how hard they are.


Too hot an environment leads to easier degassing of the coffee beans. Keeping beans in a cool cupboard or pantry is best rather than somewhere warmer in the kitchen like next to the stove.


The older the beans are, the more time they have has to release their gasses. This is why old beans have less flavor and smell compared to fresh coffee. To get the very best out of your coffee it’s best to buy it in small batches, fresh from a local coffee roaster.

Water pouring into some blooming coffee

How Much Water To Use

The amount of water you use to start the coffee blooming process should equal the amount of coffee you’re using. This is a 1:1 ratio of grams of water to grams of coffee. This value doesn’t vary between brew methods but you do want to make sure you have evenly coated all the coffee. Using a gooseneck kettle will give you more control over your pour as the water flows out the spout in a slower, more even, laminar flow.

How Long To Bloom

Bloom time is a widely debated value that can vary from 15 seconds to 90 seconds depending on who you ask. The appropriate length of time to wait for your coffee to bloom does depend on the brew method and volume of coffee you’re making, but if you’re not sure how long to wait then 30 seconds is a perfect average bloom time.

What Temperature To Bloom

The perfect water temperature to allow for optimal blooming is water that falls anywhere between 195-205F. Some people prefer to use cooler water but the majority consensus is around 200F. You can use a thermometer to check that the water is perfect or you can boil the kettle and leave it for around a minute to cool to this temperature.

Brew Methods and bloom

Pour Over

Pour-over coffee made using devices like the Chemex and Hario V60 is the perfect way to witness the delightful coffee bloom. Once you’ve weighed your coffee straight out of the grinder place the device on a coffee scale and pour the same volume of water over the coffee in a circular motion from the center of the funnel moving outwards.

Pour-over is best left to bloom for 40 seconds to a minute depending on the volume of coffee you are brewing. Once it’s settled, you can gently pour the rest of the hot water over the grounds.

French Press

The French press is another very simple way to watch your coffee bloom. Once you’ve poured the equal parts of water over the coffee and allow it to sit for 15-20 seconds. Top it up with the rest of the water and let it sit for 4 minutes to allow the flavors to infuse.

More on French Press bloom here.


Blooming is the easiest to achieve using the Aeropress inverted method. Fix the plunger in place and turn the press upside down. Add a heaped scoop of coffee and pour enough water over this to reach the 3 mark.

Let it bloom for 30 seconds and then use the paddle to stir. Top it up with water to the top of the chamber and screw the cap and filter in place. Let this sit for 1 minute 30 seconds.

Next, place your mug over the end and invert the whole device. Press the plunger to direct coffee straight into your cup.

Drip Coffee Maker

To allow coffee to bloom in a drip machine, by far the easiest way to do this is to purchase a machine that does it for you. The Techivorm Moccamaster, BUNN, Breville, Bonavita, KitchenAid, Oxo, and Cuisinart all have models that can do this automatically.

If you already have a drip machine that doesn’t perform this process for you then you can do it manually. All you need to do is add the correct volume of water that matches the weight of coffee used and start the machine as you usually would. This will soak the grounds and allow them to bloom. Wait 45-90 seconds and then add the rest of the water and turn the machine on to brew again.

Moka Pot

The Moka pot is a unique brew method that does not require coffee blooming. The water passes through the coffee very quickly so does not require you to bloom it first. You can pre-heat the pot before you use it but the coffee should be added dry.


Espresso is usually considered a brew method that doesn’t require the coffee blooming stage. As with most coffee brew methods, there is a way to add a similar bloom effect when brewing an espresso. This process is called pre-infusion and it coats the puck of coffee with hot water before the machine brews the espresso. As well as allowing some coffee blooming, it also allows the water to more evenly penetrate the coffee and gives a better flavor extraction.

Pre-infusion can be done using a specially designed espresso machine or you can do it using a manual espresso maker.


Coffee blooming is a key stage in the brewing process to help maximize flavor in your java. It’s easy enough to do and pretty fun to watch as the coffee bubbles and swirls around. A lot of factors can affect how ‘bloomy’ your coffee will behave and not every brew process requires this step.

Best of luck with your coffee making journey and happy blooming!

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