I am a fan of pour-over, generally speaking, and I understand the importance of wetting the grounds, then allowing them to "bloom" for 45 30 seconds or so before beginning the extraction. The main purpose of this is to allow carbon dioxide and other gasses to escape from the grounds, so they can extract more evenly.

I have a coworker who is a fan of French Press, and he does a bloom in the French Press as well. I'm curious if this matters as much in this context, since the grounds are completely submerged the whole time. Is it important? If so, is it for the same reason or some other reason as a pour-over?

  • 3
    Has anyone shown any research that the bloom is truly for letting the gasses escape or to provide for saturation of the grounds and does it make a difference for pour-over or other brewing methods?
    – daustin777
    Commented Apr 7, 2015 at 3:01
  • 1
    45 seconds? Hmmm, I've always done 30.
    – NealC
    Commented Jun 15, 2015 at 5:06

3 Answers 3


I believe there is mysticism to blooming. Don't get me wrong, I feel its important, but I don't think it does all the things that people claim it does. Blooming is important when using fresh roasted beans(and you should be). Blooming simply aids in removing CO2 from the grounds, which would otherwise create negative space between your grounds and the water. It's simply used to provide a more even extraction. Blooming is important in any immersion brewing, and can even aid in pour-over methods as well.

You should also reduce your brew time slightly to compensate for the extraction that takes place during the bloom. I'd typically bloom for 30 seconds, then push the bloom down gently without agitation(agitation effect solubility).

I think its a dubious claim to state that the bloom does anything beyond removing the CO2, thus providing a more even extraction. It would really depend on how you perform your bloom. Do you bloom then start your timer? Do you bloom with a small amount of water first, then add more to prevent too much extraction during the bloom? Ultimately these differences in taste don't have anything to do with the bloom itself, but more so the extraction time brought on by how you perform your bloom.

The bloom itself does not effect taste, and it is an important part of using a french press, as its key to providing even extraction.

  • You are really contradicting yourself here. If the Bloom is necessary for an even extraction, it does definitely affect taste. Why? Because an uneven extraction means over or under extraction or even both at the same time. That will have a noticeable effect on taste. Furthermore, in my opinion the bloom is quite important in pour overs, as it allows removing the gas before adding more water and before the water actually drips through the filter. Then you add more and the grounds get evenly extracted. In full immersion methods the need to bloom is certainly less clear.
    – avocado1
    Commented Mar 21, 2018 at 15:49

It's going to produce a stronger brew and probably more oils, likely resulting in more crema.

What you're essentially doing is heating the grinds, starting the extraction process a bit and then giving a small amount of hot water about 30 seconds to cool before adding more - very similar to what pre-infusing a puck in an espresso machine would accomplish.

Does it matter? It could conceivably affect taste, so yes. The extent that it might affect the flavor of the coffee would vary quite a bit depending on the beans, water and ground - but it will produce a difference in taste you can probably measure just by sampling in all but very dark roasts.

For gas levels - you would have to pour very carefully to avoid air bubbles as much as possible and observe, and I'm not even sure you could detect it.

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    Crema is a terminology that is confined to espresso. You do not produce crema with a french press, and its not something I'd consider a sign of good or properly french pressed coffee. Though I wouldn't really deem it a poor trait either, its simply not a significant factor in french pressed coffee, as it is in espresso.
    – tsturzl
    Commented Jun 12, 2015 at 0:22

In regards to non-espresso "crema," the one thing it does tell is the freshness. A coffee roasted 2 days ago will have much more than a month old coffee that's been on the shelf.

  • But to what extent does it matter in the blooming process?
    – JJJ
    Commented Dec 13, 2019 at 6:15

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