winnows

Winnows are devices or processes used to separate lighter chaff from heavier grain by using wind or air currents. The term can refer to both the action of winnowing and the implements used to carry it out. In its simplest form, a winnow is a shallow, flat basket, tray, or mat with a handle. Grain is placed in the winnow and repeatedly lifted and tossed into the air; the wind blows away the lighter chaff while the heavier kernels fall back for collection. This method relies on a favorable breeze and is commonly used with crops such as wheat, rice, barley, millet, and sorghum.

Mechanized winnowing systems are used in many processing chains. A winnower or wind winnower uses an artificial air flow from a fan or blower to separate particles by density. After threshing, air streams loosen plant material; sieving may follow to remove remaining chaff and dust. Modern grain-cleaning equipment may combine winnowing with aspirators, sieves, and cyclones, enabling large-scale separation with greater consistency and speed.

Winnowing has a long history and has been practiced in many cultures around the world. In traditional agriculture, the technique is valued for its simplicity and minimal equipment, though it depends on weather and local grain characteristics. Etymology derives from the Old English winnian, related to separating impurities from grain.

See also: threshing, seed-cleaning equipment.