Floaters are coffee that has been separated by buoyancy. The word “floaters” is often used in conjunction with “overripes.” While it is generally true that overripe coffee constitutes the majority of the floaters, the hydraulic separation process separates the coffee not by maturation state, but rather by buoyancy. In fact, coffee in unripe and ripe maturation states often is found in the floaters.
The buoyant force exerted by water or other fluid on an object is equal to the weight of the water displaced by the object. Therefore an object with a density greater than that of the fluid in which it is submerged tends to sink.
The basic formula for density is: Density = Mass/Volume
Here is a classic science experiment to demonstrate buoyancy. Though the volume of the cans is the same, the regular Pepsi contains high-fructose corn syrup (hfcs). Since artificial sweetners such as aspartame and saccharin are much more potent than sugar and hfcs, less is used and the product thus weighs less per unit of volume. Judging by the Pepsi cans we can see that this principle of physics has been true for quite some time 🙂
THE SEPARATION PROCESS
Here is how the coffee is separated by density after it is harvested:
All states of maturation can be floaters:
Since overripe coffee has less moisture, it has less mass/volume and floats
Since underdeveloped and damaged beans have less mass per volume, they float
UNRIPE AND RIPE FLOATERS
Within the set of floaters is the subset of unripe and ripe fruit. When these fruits develop properly, their density will cause them to sink in the hydraulic separator. However, when the development process is altered or when the seeds are damaged, such as seeds that have been attacked by the coffee bean borer, the density of the fruit is lessened thus causing it to float.
TYPES OF OVERRIPES
Overripe coffee generally constitutes the largest subset of floaters and can be divided into
- dried on tree (DOT),
- overripe raisin coffee (past prime maturation but not completely dried), and
- small dried coffee called “coquinhos” here in Brazil (smaller sized fruit that went directly from unripe to overripe).
Since coquinhos have a strong taint of burnt rubber, they should be removed to maxmize quality.