Winnowing

Winnowing is the method in which heavier particles are separated from lighter particles by using wind/blowing air.
This technique is used most commonly when we need to separate the grains from chaff. Mostly used by farmers or people associated with wheat or flour businesses.

Process: Grains collected from the fields contains dirt, dust, husk, chaff, etc along with grains. First of all, chaff is separated from the grains by the process of threshing. Then, the grains are dropped from a height. The lighter particles are carried away from wind while the heavier particles fall vertically downward.

Advantages:

1. No machinery is needed.
2. With modern technologies, table fans can be used for this process, if air is not blowing.
3. It is a cheap method.
4. It is less time-consuming.

Disadvantages:

1. Wind or blowing air is needed.
2. The process is useful only when the weight of the substance is such that wind can move it. For example, if we have to separate small stones from grains, then stones being heavier, will not be carried away by the wind.