What is floating in coffee processing?

Floating is a quality sorting technique in which freshly harvested coffee cherries are placed in water - either a tank, channel, or trough - and the resulting buoyancy difference is used to separate high-quality dense cherries from defective or underripe ones. Dense, fully ripe cherries sink; underripe, dried-out, overripe, or insect-damaged cherries are less dense and float to the surface where they can be skimmed off and removed.

Floating is typically performed immediately after harvest and before depulping or other processing begins. It's a simple, low-cost quality control step that removes a significant proportion of defective material before it enters the main processing stream - improving consistency and reducing the likelihood of defect notes in the final cup. At some washing stations, floating is done in channels where water flow also moves cherry along to the depulper.

The technique has limitations: floating sorts by density, not by ripeness per se, so some uniformly dense but slightly underripe cherry may sink alongside perfectly ripe fruit. It's most effective when combined with selective hand-picking rather than used as a substitute for it. Floaters removed from the tank are either composted, processed separately as a lower-grade lot, or in some origins dried and sold as a separate stream.