Winnowing is a process by which chaff is separated from grain. It can also be used to remove pests from stored grain. Winnowing usually follows threshing in grain preparation. 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.
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 mysticized 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 the Odyssey, the dead oracle Teiresias tells Odysseus to walk away from Ithaca with an oar until a wayfarer tells him it is a winnowing fan (i.e., until Odysseus has come so far from the sea that people don't recognize oars), and there to build a shrine to Poseidon.
Fengshanche
In ancient China, the method was improved by mechanization 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 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.
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vignette|Batteuse moderne simple à riz paddy. Le batteur bien visible représente l'essentiel de la machine. Une batteuse est une machine agricole servant à battre les céréales à poste fixe pour séparer le grain de la paille et de la balle ou faluns. Ces opérations, battage, secouage, vannage, évacuation de la paille et des faluns, effectuées à l'aide de fléaux, de fourches et de cribles pendant des siècles, étaient un travail éreintant prenant un temps considérable ; la batteuse les effectue simultanément et rapidement.