TL;DR: The bloom is CO₂ escaping from freshly roasted coffee. Skip it, and gas bubbles create channels preventing even extraction. A 30–45 second bloom with 2x coffee weight in water is ideal.
Where CO₂ Comes From
During roasting, Maillard and caramelization produce CO₂. Grinding accelerates degassing — pre-ground coffee barely blooms.
During the Bloom
Hot water heats trapped CO₂, causing it to expand and escape. Hotter water releases ~35% more CO₂.
Why It Matters
Gas bubbles form barriers between water and coffee. Escaping gas creates channels — some areas under-extract, others over-extract.
The Protocol
Pour 2x coffee dose in water, wait 30–45 seconds until bubbling stops, then continue.
Try This
Brew coffee at 3 days post-roast (aggressive bloom) and 3 weeks (flat bloom). Taste both. The sweet spot is 10–14 days.
