Blooming is not usually a word most people connect to coffee brewing, but it’s actually a key concept. To understand what blooming is and why it is important, you need to know a little about coffee roasting.
Roasting To "Degassing"
During roasting, coffee undergoes chemical reactions—complex carbohydrates are broken down into smaller molecules, beans begin to brown, and lots of carbon dioxide is created inside the bean. After roasting, the CO2 will continue to slowly leak out of the beans for the next few weeks. This process is called “degassing”.
Coffee and Carbon Dioxide
Coffee has an interesting relationship with carbon dioxide. Too much in the bean will make it taste sour, but too little (or none) will make it taste flat. And, CO2 repels water, so it can actually prevent coffee and water from connecting. Getting enough CO2 out to connect our coffee and water while still keeping enough in to ensure flavor is where blooming comes in.
How To Bloom
Pour a small amount of hot water onto your grounds (enough to cover them), let them "bloom" (bubble and froth) for 30 seconds, then brew as usual. Pouring hot water onto fresh coffee, speeds up the "degassing process", so by doing this you release enough CO2 so that your water and coffee can now truly connect. Better connection means even extractions which leads to better tasting coffee—always the goal!
One note: if your grounds do not bubble up when you bloom- it's most likely that they have no CO2 left, which happens with old coffee. The older coffee gets, the more flat tasting it will be. That’s why we always recommend using freshly roasted coffee—it ensures a lively, tasty cup.