Coffee – What makes coffee grinds sink in a french press

coffeefrench-press

We use a press pot to make coffee at home, and usually after a 3 minute steep, the grounds are floating at the top, but with this one bag of beans we got, they're all sunk to the bottom.

The coffee basically tastes normal. Maybe a little thin, but that could easily be the roast.

Why would most coffee grounds float, but these sink? Is there something wrong with these beans?

We use a burr grinder and hadn't changed the grind setting. Same water, etc. Only change is the beans. "Medium-Dark" roasted Ethiopian Yirgacheffe from a local roaster, roasted about 2 weeks before brewing…

Best Answer

Coffee beans contain gases, which causes coffee to float.

  1. Fresh coffee contains more gases compared to an older (aged) coffee.

    • coffee tastes best between 4 - 14 days off roast, varies depending on roast profiles
    • Specialty coffee shops usually have a roast date on their retail bags
  2. On a coarse grind setting each particle hold more gases compared to a fine grind setting which hold less gases.

  3. Hot water causes a faster release of gases compared to cold water which causes a slower release of gasses

  4. Darker roasts hold less gases compared to a lighter roast.

  5. A lot of agitation increases the rate in which gasses release compared to no agitation.

All these can be easily tested, and affect how long the coffee stays afloat.

Gasses in the coffee particles must first be displaced in order for the water to enter each particle and extract a delicious cup. All in all, it doesn't matter why, as long as the coffee tastes good.

Late reply but thought I'd clarify.