Wind winnowing is an agricultural method developed by ancient cultures for separating grain from chaff. It is also used to remove weevils or other pests from stored grain. Threshing, the separation of grain or seeds from the husks and straw, is the step in the chaff-removal process that comes before winnowing. "Winnowing the chaff" is a common expression.
In its simplest form it involves throwing the mixture into the air so that the wind blows away the lighter chaff, while the heavier grains fall back down for recovery. Techniques included using a winnowing fan (a shaped basket shaken to raise the chaff) or using a tool (a winnowing fork or shovel) on a pile of harvested grain.
Winnowing can also describe the natural removal of fine material from a coarser sediment by wind or flowing water, analogous to the agricultural separation of wheat from chaff.
In Greek culture 
The winnowing-fan (λίκνον [líknon], also meaning a "cradle") featured in the rites accorded Dionysus and in the Eleusinian Mysteries: "it was a simple agricultural implement taken over and mysticised by the religion of Dionysus," Jane Ellen Harrison remarked. Dionysus Liknites ("Dionysus of the winnowing fan") was wakened by the Dionysian women, in this instance called Thyiades, in a cave on Parnassus high above Delphi; the winnowing-fan links the god connected with the mystery religions to the agricultural cycle, but mortal Greek babies too were laid in a winnowing-fan. In Callimachus' Hymn to Zeus, Adrasteia lays the infant Zeus in a golden líknon, her goat suckles him and he is given honey.
In China 
In Ancient China the method was improved by mechanisation with the development of the rotary winnowing fan, which used a cranked fan to produce the airstream. This was featured in Wang Zhen's book the Nong Shu of 1313 AD.
In the New Testament 
In the Gospel according to Matthew 3,12, a sentence introduces the separation of wheat and chaff (good and bad) by "His winnowing fan is in his hand" (American Standard Bible and New American Bible translation). The New International Version and the New Revised Standard Version translate the term as "winnowing fork."
In Europe 
In Saxon settlements such as one identified in Northumberland as Bede's Ad Gefrin  (now called Yeavering) the buildings were shown by an excavator's reconstruction to have opposed entries. In barns a draught created by the use of these opposed doorways was used in winnowing.
The technique developed by the Chinese was not adopted in Europe until the 18th century, when winnowing machines used a 'sail fan'. The rotary winnowing fan was exported to Europe, brought there by Dutch sailors between 1700 and 1720. Apparently they had obtained them from the Dutch settlement of Batavia in Java, Dutch East Indies. The Swedes imported some from south China at about the same time and Jesuits had taken several to France from China by 1720. Until the beginning of the 18th century, no rotary winnowing fans existed in the West.
In 1737 Andrew Rodger, a farmer on the estate of Cavers in Roxburghshire, developed a winnowing machine for corn, called a 'Fanner'. These were successful and the family sold them throughout Scotland for many years. Some Scottish Presbyterian ministers saw the fanners as sins against God, for wind was a thing specially made by him and an artificial wind was a daring and impious attempt to usurp what belonged to God alone.
In the United States 
In sedimentology 
Winnowing can also describe the natural removal of fine material from a coarser sediment by wind or flowing water, analogous to the agricultural separation of wheat from chaff. Once a sediment has been deposited, subsequent changes in the speed or direction of wind or water flowing over it can agitate the grains in the sediment and allow the preferential removal of the finer grains. This action can improve the sorting and increase the mean grain size of a sediment after it has been deposited.
See also 
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- Harrison, Prolegomean to the Study of Greek Religion, 3rd ed. (1922:159).
- Karl Kerenyi, Dionysus: Archetypal Image of Indestructible Life (1976:44).
- The Question of the Transmission of the Rotary Winnowing Fan from China to Europe: Some New Findings, Hans Ulrich Vogel, 8th International Conference on the History of Science in China
- Münzenberg, Hessen. Chapel and Palas (G.Binding, Burg Münzenberg, 1962)
- M.W.Thompson, The Rise of the Castle, (Cambridge University Press, 1991), 5-6.
- Broadcasting and winnowing, Antique Farm Tools
- Robert Temple, The Genius of China, p. 24
- Chambers, Robert (1885). Domestic Annals of Scotland. Edinburgh : W & R Chambers. p. 397.
- Compton, R. R., 1962, Manual of field geology, John Wiley & Sons, 378 p.