If you’ve ever looked up a pour-over recipe on the internet, you’ve no doubt encountered the phrase “blooming.” Some of the more technical coffee brewing literature calls it “wetting” or “prewetting.” But it all refers to the same thing: saturating the coffee grounds and waiting for a short period before starting the rest of the brew. Typically, the blooming stage takes around 30 seconds, though it can vary based on the freshness and roast degree of the coffee.
Why do we Bloom?
Blooming is meant to accomplish two things.
1. De-gas the coffee. Fresh coffee contains trapped carbon dioxide from the roasting process. This escaping CO2 is what causes the blooming effect. It also tastes bitter and interfers with the extraction. So even though carbon dioxide shows us the coffee is fresh, we want to remove as much as possible.
2. Saturate the coffee. The soluble compounds in coffee will extract more readily once the grounds are fully saturated. Blooming gives the ground coffee a chance to absorb water.
How do we Bloom?
The secret to blooming a pour-over is making sure all of the grounds get wet. It sounds simple enough, but actually takes some practice. Every barista has had the experience of seeing a dry pocket of grounds come bubbling up to the surface well into the brew. When this happens you can be sure there will be uneven extraction.
Personally, I find a a brisk spiral pour is the easiest way to wet the grounds evenly, but there are a variety of techniques that are worth experimenting with.
Because ground coffee can absorb roughly double its mass, we recommend blooming with at least 2.5 times your dose. This means if I’m making a 60 g / 1L batch with the Etkin Dripper I’m going to use at least 150 g of water to bloom the coffee.
Some commercial coffee brewers give the user the ability to control the bloom with what they call the “prewet percentage.” This refers to how much of the total brew volume is used for wetting. In the above example a 150 gram bloom would be expressed as a 15% prewet percentage.
Does it Matter?
An easy experiment to see why blooming matters is to make three pour-overs. With the first, skip blooming altogether. With the second, bloom with only 1.5x the dose. With the third, bloom with 2.5 x the dose.
I’ve repeated this experiment dozens of times in the coffee classes I teach, and the results are always the same. In a blind taste test, practically everyone prefers the third cup.
A Simple Test
Interestingly, I often find pour-overs made without a blooming stage taste better than pour-overs that were brewed with an insufficient or poorly executed bloom. If you don’t mind wasting some coffee, there’s an easy experiment to test the effectiveness of your blooming technique.
Bloom the coffee as you normally would, but instead of continuing the brew after 30 seconds carefully remove the filter from the dripper and place it on a plate. Using a chopstick to spoon, comb through the coffee grounds (careful, they'll be hot). If you find any dry pockets you know that your pouring technique still needs some work. If all of grounds are wet, congratulations, you have successively bloomed your coffee!
Shaken not stirred?
The best way to apply turbulence during the blooming stage is a matter of some debate. Some advocate a swirl, other stirring with a wooden spoon (please don't use a metal spoon to stir the Etkin Dripper!)
Although the double walled design of the Etkin Dripper makes swirling a breeze, if you pass the aforementioned filter test, I don't think either swirling or stirring is necessary. Simply pouring briskly applies a lot of turbulence to the brew bed.
But that's just my opinion. The beauty of making coffee is that there is no one right way to do. Experiment, be creative, and test your hypothesis with a blind tasting.
Please don't hesitate to share the results with us on Instagram or email me at michael at etkincoffee.com.