What is a floater in green coffee?

A floater is a defective coffee bean with abnormally low density - it floats to the surface when placed in water. That low density indicates the bean is hollow, underdeveloped, or damaged, lacking the cellular mass of a properly formed seed.

Flotation is one of the simplest effective quality control steps in processing. At cherry intake or post-pulping, placing beans in water lets floaters be skimmed off before they enter fermentation or drying. Well-developed beans sink; floaters rise. It takes minutes and removes a significant source of defects upfront.

Floaters are typically caused by Coffee Berry Borer damage, underdeveloped cherry harvested too early, frost, or disease. In the roaster they stay pale - effectively quakers - and contribute grassy, papery, or hollow notes to the cup. If they make it through processing and sorting, they're a real quality problem.