Everything You Need To Know About Blooming Coffee

While it's easy for people to see brewing as a push-button task, expert brewing involves a multitude of details. It involves selection among a wide range of brewing vessels, advanced techniques, and — most important – coffees before you ever get to the interaction between water and bean. But before diving into such selections, it's important to become well-versed in foundational techniques.

One such foundational technique is blooming, a method of degassing beans. So to aid in comprehensively understanding this method, Chowhound has exclusive advice from Andrea Allen, coffee expert and co-founder of celebrated Arkansas cafe Onyx Coffee Lab (Instagram). As the 2020 U.S. Barista Champ and 2021 World Barista Runner-Up, she certainly knows the ins and outs of coffee brewing.

She notes that blooming is a straightforward process you conduct at the beginning of the brewing process. It entails pouring a small amount of hot water over your coffee before the brewing begins. Allen points out that the step pays off in several ways, both minimizing carbon dioxide's acidic effect on flavor and helping promote uniform extraction. Especially since it requires only 30 seconds, it's undoubtedly worth the time investment.

While the term "blooming" may sound intimidating, the process is straightforward. It simply requires hot water — which you need for brewing anyway — to cover the coffee grounds. The maneuver causes carbon dioxide contained in the beans to escape, Allen explains. This gas initially forms inside the coffee during the roasting process. Initially, the concentration is high — the reason you don't want your coffee too fresh — and gradually leaks from the beans. 

To ensure this gas expulsion occurs, Allen recommends pouring a small but even amount of water. The exact amount varies based on the preparation method and coffee quantity. Common advice is to incorporate double the volume of grounds. However, it's most important to ensure all the coffee is completely submerged. You can't just cover the entire surface area (though you should), you must also ensure water goes all the way down so there are no dry grounds. It's easy to miss spots in a pinch, so keep an eye on water-coffee contact. That's why you should agitate the coffee-water mixture during blooming. 

The degassing of coffee requires a moment of patience. Allen recommends giving the bloom the industry-standard 30 seconds. That's enough time for most of the gas to release, which you'll see in the form of bubbling that dies down toward the end of the blooming period.

Nevertheless, there's no such thing as blooming for too long. In fact, the longer the grounds sit in water, the more thorough the gas elimination, so some baristas suggest waiting for up to 10 minutes for the process. While that's not typical, it's a helpful reminder that it's okay to extend the process. Plus, starting with moist grounds leads to better extraction, a reason you should always wet your coffee filters.

During this process, some baristas recommend swirling the pour-over vessel to eliminate further gases, while others swear by carefully stirring the mixture. Such small details impact the flavor, but they're not nearly as paramount as carrying out the bloom to completion.

Blooming is a noticeable physical process with an accompanying visual effect. You'll see quite a bit of bubbling right when you start the process. As Allen explains, "The bloom looks like the coffee rising or 'puffing' up," a sure sign of gas leaving. And while bubbles are the most prominent reaction, she says that certain coffee varieties may also appear lighter. 

Such signs of degassing are especially prominent with freshly roasted grounds.  If abundant bubbling is happening, then there's still more gas to release. As a result, inspect the action to judge blooming time. If 30 seconds have gone by and there's still foaming, then keep blooming. Allen explains that available carbon dioxide is only released once you stop seeing any signs. So keep an eye on visual cues to ensure you're carrying out the technique to completion rather than setting a timer.

Although blooming seeks to expel carbon dioxide, its presence in coffee is actually beneficial. Retaining the gas during storage ensures the beans aren't exposed to oxygen, thereby lengthening their storage time. It's the reason roasters often seal their freshly roasted beans in a bag with a one-way valve, which allows carbon dioxide to get out but doesn't allow oxygen in. And it also speaks to the importance of keeping coffee in an airtight environment and why it's sometimes a mistake to store coffee beans in the bag they came in.

In fact, Allen recommends keeping an eye on the blooming to ascertain the bean's freshness. She notes that if there are no bubbles or the coffee doesn't puff, it's likely your coffee is stale. As a result, this first reaction with water is a telling assessment of the potential of your brew. So when purchasing beans, Allen reinforces the importance of checking the roast date, noting it's a crucial detail when inspecting a coffee bean label.

Whether you're making an iced or hot pour-over, the blooming process is equally essential. However, Allen notes that hot water is essential to expelling the carbon dioxide. As a result, it's tricky to know the course of action with a cold-brewing method. If you're using a coffee-making style that calls for cold water, Allen advises that you can still try the method with the caveat that the "bloom will be less impressive because it is the heat that activates the carbon dioxide." 

But you can still try blooming your coffee with cold water. In fact, some baristas experiment with the cold-bloom method to purposefully minimize extraction, thereby reducing burnt and acidic flavors as well as affecting the color of the coffee. To cold-water bloom, you do essentially the same thing as a regular bloom but using room-temperature water. You just can't expect the same dramatic results from the bubbling, which can make it tricky.

For better results, Allen suggests relying on the standard blooming method and crafting a flash brew instead. This coffee-making style brews the grounds with hot water as usual, but rather than dripping into an empty carafe, it drips over ice, thereby cooling the coffee immediately after extraction. The aromas of the iced product are still intact; however, the bloom occurs without issue — a definite win. The method's success proves its essential nature. Blooming is imperative to get the most out of a coffee brew.