Coffee Facts: What is the Bloom?

You might have heard coffee enthusiasts talk about the “bloom” when brewing coffee and found yourself momentarily confused. Don’t worry, we got you. When freshly ground coffee is brewed, you may notice that the water and grounds start to swell and bubble up (we like to say it looks like a wet brownie!) – this is what people refer to when they talk about the bloom. And it’s a good thing to have! 

Once roasted, coffee beans trap carbon dioxide in their shells which start to slowly dissipate in the days and weeks after. This process of degassing is natural– whole beans de-gas at a much slower rate than pre-ground coffee beans, which is why aficionados often tout the virtues of only buying whole beans and grinding just before brewing. Ground coffee de-gasses quickly, so if you don’t drink it in a timely manner, the resulting brew can taste more mellow since much of the flavor comes from the oils and carbon dioxide molecules. 

Back to the bloom: if you have coffee that blooms, that is a sign of freshness. The gas inside of the beans interacts with hot water to release during the extraction process, resulting in a cup with retained flavor and aroma. Gas is your friend, look for it! What’s important to do when faced with a bloom is to let it be. The gas needs to be released, so don’t tamp it down or push it into the cup– that can result in a sour brew due to improper extraction.

To recap, a coffee bloom is the swelling that occurs when hot water and freshly coffee grounds interact during the brewing phase that indicates the freshness of the coffee through the release of stored carbon dioxide and oils. Some blooms are bigger than others, and some are longer than others. Regardless, a bloom is a good thing to have and a sight to behold in and of itself. Now that you’re up to speed with coffee lingo, you can boast to your friends about all your beautiful blooms. 

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Learn about dialing in a phin filter here. 

Learn how to brew high-caffeine coffee here.