Bloom
The 30–45 second pre-pour stage where a small amount of hot water lets fresh coffee degas before the main brew. The bubbling foam on top is the bloom in progress.
Bloom is the initial pour in pour over brewing where you wet the grounds with roughly twice the coffee's weight in water (e.g. 30 g water for 15 g coffee) and wait 30–45 seconds before pouring the rest. The trapped CO₂ from roasting escapes during this pause, allowing the main brew to extract evenly.
Why bloom matters
Freshly roasted coffee contains carbon dioxide trapped inside the cellular structure. When hot water hits the grounds, that CO₂ releases as visible foam. If you don't bloom, the CO₂ release happens during the main pour — and the gas pushes water away from the grounds, causing uneven extraction and a thinner cup.
Bloom lets the gas escape first. The grounds are then ready to extract evenly when the rest of the water arrives.
Standard bloom recipe
- Water: 2× the dose by weight. 15 g coffee → 30 g bloom water.
- Time: 30–45 seconds.
- Technique: Pour slowly to wet all grounds; optional swirl or gentle stir to ensure full saturation.
- Then: Continue with the main pour sequence.
Bloom by coffee age
Freshness changes how vigorously the bloom rises:
- 1–5 days off roast: Aggressive bloom, large dome, may need longer time (40–50 s) to settle.
- 7–14 days off roast: Standard bloom behavior. Most pour over recipes are tuned for this window.
- 21+ days off roast: Weak or non-existent bloom. Less CO₂ left; shorter bloom time (20–30 s) is fine.
- Decaffeinated coffee: Often blooms less because processing affects gas retention.
Does espresso need a bloom?
Pre-infusion in espresso machines is the equivalent concept — a short, low-pressure wetting phase before the full 9-bar pressure ramps up. Decent, Lelit Bianca, and similar machines let you program pre-infusion explicitly; many entry-level machines apply a brief soak automatically.
Related terms
- Days Off Roast — determines how vigorous the bloom will be.
- Channeling — uneven extraction that bloom helps prevent.
- Brew Ratio — the bigger picture the bloom water is part of.
Log every step of your pour over.
Multi-step recipes with bloom timing saved per brew.
