Degassing (Outgassing)

During roasting, coffee beans absorb large quantities of CO₂ inside their cell structure; degassing (also called outgassing) is the gradual release of this gas once the beans leave the drum. The process is most intense in the first 3–7 days post-roast, then slows over the following 2–4 weeks. Using coffee before sufficient degassing causes practical problems: in pour-over and immersion brewing, excess gas creates turbulent blooms that impede even extraction, while in espresso, the unstable CO₂ produces an irregular, short-lived crema. Most roasters recommend a rest period of at least 3–5 days for filter and 7–14 days for espresso before brewing.