Blooming Coffee 101

Why You Should Be Blooming Coffee!

Blooming Coffee - What is it?

Blooming is a rapid release of Carbon Dioxide (CO2) and other gases from coffee grinds immediately after they come in contact with hot water.

Let’s back up for a second and look at the entire process.


When organic materials are heated, a number of reactions occur and various volatile compounds are released in gaseous form.

In this context, the process of roasting coffee beans involves the production of a number of volatile compounds, including CO2. Most of these gases are released throughout the roasting process, but some remain trapped within the beans.

Whole Bean

The gases that are stored within the beans slowly escape over the course of about 2 weeks. This is referred to as degassing.

Ground Coffee

After grinding the beans, CO2 and other volatile compounds are released in gaseous form at a drastically increased rate. This is due to the increase in surface area of the coffee.

So why does any of this matter? ...

Do we want CO2 in our coffee? Do we NOT want it in our coffee? Well, actually..

We want CO2 and other gases to remain in our coffee UNTIL we begin brewing.

I understand that this seems a little bit convoluted, but bear with me.

After roasting and before brewing, the retention of these gases helps to prevent the deterioration of flavor compounds within the beans. This is why coffee it's recommended to grind immediately prior to brewing.

After grinding, when we begin brewing, we then want the CO2 out of the picture, because it repels water and interferes with the extraction of flavor compounds. Too much CO2 in your cup can also cause your coffee to taste a bit sour.

So how do we adhere to this rather specific time frame?


Blooming Coffee

The addition of hot water to the grinds increases the rate of gas release even more than the process of grinding.

If you add all of the water that you're brewing with at once... that is to say, if you do NOT BLOOM;​​

1. The release of CO2 is partially inhibited. This in itself can cause your coffee to be sour. 

2. As the gases bubble and attempt to liberate themselves from your drink, they actively interfere with the ability of the water to extract flavor compounds from the grinds.

Basically, if you don’t allow your coffee to bloom, you’re risking an under-extracted, possibly sour brew and missing out on a more developed flavor!

By adding just enough water to cover the coffee grinds and allowing a short time to bloom, gases are able to rapidly escape. This removes CO2 from your brew, and also allows for optimal extraction of flavor compounds.

To summarize;

Blooming Steps Flowchart

Factors That Affect Blooming

It probably goes without saying, but degassing and blooming are intimately related. If significant degassing has occurred, a less significant bloom will occur. If minimal degassing has occurred, blooming may be very evident.

The Freshness Factor

As we mentioned, natural degassing occurs for about 2 weeks after the coffee beans are roasted. This is why some roasters incorporate degassing valves into their coffee bags. This is also why some companies offer products that are roasted to order, (so you can get them before that 14-day window is up).

While blooming will never hurt, it also won't have much of a positive impact if you’re brewing with coffee that isn’t fresh!

At the end of the day, coffee that isn’t fresh isn’t going to bloom. If the beans being used were roasted more than 2 weeks before brewing, there may be little to no gases left to be released.

Storage Temperature

As a general rule of thumb, heat increases the rate of reaction. In this case, the reaction is the release of volatile compounds in gaseous from.

Therefore, storing your beans in a warmer environment will increase the rate at which degassing occurs. That is to say, you should store your beans in a cool environment and ideally away from direct exposure to light.


Humidity refers the the amount of water vapor present in an environment. Water vapor is gaseous. Without getting insanely complex, more water vapor in an environment =  less room for the addition of gases.

So a more humid environment will result in less degassing than a particularly dry one. Of course, if you go too far in the humidity direction, you’ll risk mold and damage induced by water vapor… honestly, just store your whole bean coffee in a sealed container in a cupboard.

Roast Level

As a general rule of thumb, darker roasted beans will have more CO2 trapped within them after roasting. As darker roasts reach higher temperatures and often have a longer roasting duration, more CO2 is produced. The beans also expand more, creating the spaces in which gases become trapped.

Bean Hardness

The harder the bean, the more difficult it is for gases to escape. Typically, beans that are grown at higher altitudes are harder and more dense.

You don’t really have any control over this, but it’s something to be aware of if you’re comparing blooms from bean to bean.

Bean Origin

Beans from different origins result in different degrees of blooming. Differing growing conditions and the resulting variance in bean size, shape, density and hardness can all have an impact on blooming.

How to Bloom Your Coffee

Luckily for us, blooming is quite easy, requires very little time and no additional equipment.

The process involves adding just enough hot water to cover the coffee grinds, and allowing a short period of time to pass before adding the remainder of the water.

The exact way to complete this process depends on your brewing method of choice.

French Press Coffee

Add just enough hot water to cover the coarsely ground coffee. Allow it to sit for 20-30 seconds, and then gently mix. Try to ensure that all of the grinds come in contact with the water. Add the rest of the water immediately after!

Pour Over Coffee

Starting from the outside walls, gently pour hot water in a circular motion, slowly moving in toward the center. The goal is to uniformly soak the coffee without allowing it to drip through the filter. Allow the soaked grinds to sit for about 60 seconds before continuing. This can take a little bit of practice, don’t worry if there’s some drip through on your first try!

Auto Drip Coffee

Add just enough hot water to cover the coffee grinds. The goal is to uniformly soak the coffee without allowing it to drip through the filter. Allow the soaked grinds to sit for about 90 seconds before starting the brew cycle.

Final Thoughts

Blooming coffee is quick and easy. We recommend that you get in the habit of blooming every time you make coffee! If you purchase fresh roasted coffee and grind daily, you will definitely notice the difference.

Even if you aren't sure how fresh your coffee is, blooming only takes a few seconds. Might as well give it a try!

Too much trouble? Bonavita Coffee Makers have built in "pre-infusion" AKA blooming cycles!

Here's how they work:

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