title_body: What is coffee bloom
upvoted_answer: The gases themselves are largely composed of CO2 and moisture trapped in the grinds. My understanding is that releasing the gases ahead of time prevent the gasses from interfering with an even extraction throughout the brewing process.
  
  As when brewing coffee, we're trying to expose the grounds evenly to the hot water, the release of gas fights against this, causing channeling or uneven extraction. This can affect your flavor profile by overextracting some of the coffee, and not extracting enough from the rest.
  
  From my own experience, fresher, better-quality coffees tend to produce more gasses. I would imagine this being because the gasses escape on their own over time from the coffee when it's just sitting around.