Threshing is the process of loosening the edible kernel (or wheat berry) from the inedible structures surrounding it, primarily the straw (dried stalk) and the chaff (light, flaky casings). This separation is a necessary step performed after the wheat is harvested and before the grain is ready for milling or consumption. The goal is to apply mechanical force to break the natural bond between the kernel and its protective layers, freeing the grain for collection.
Preparing the Wheat for Threshing
Proper preparation of the wheat stalks is crucial before threshing begins. Harvesting must occur when the grain reaches the “hard dough” or “flint stage,” indicated by the entire plant turning golden and the kernels becoming firm and brittle. Cutting the wheat at this point ensures the kernels are fully mature and have low moisture content, which is important for quality and storage.
Once cut, the stalks are gathered into manageable bundles called sheaves, with all the grain heads aligned. These sheaves are typically arranged into upright, teepee-like formations known as shocks, which are left in the field for several days to cure. This curing period, often lasting seven to ten days, allows the material to dry further and become brittle, making separation easier during threshing.
Manual Methods for Separating Grain
For small batches, a contained beating technique is used. The wheat heads are placed inside a sturdy container, such as a clean five-gallon bucket or a large trash can. Forcefully striking the bundles against the interior sides causes the impact needed to shatter the brittle bond holding the kernels. The freed kernels fall to the bottom, while the chaff and straw fragments remain mixed with the grain.
A more traditional method utilizes a hand tool called a flail. A flail consists of a long handle hinged to a shorter, heavier wooden piece called the swingle. The harvested wheat is spread out on a clean surface, such as a canvas tarp or a dedicated threshing floor. The operator swings the flail, causing the weighted swingle to strike the grain heads repeatedly, generating the force needed to knock the kernels loose.
Another technique, historically used for larger volumes, is treading or stomping. The material is spread across a hard, clean surface, and the operator walks repeatedly over the grain heads. This method uses crushing pressure and friction to rub the kernels free from the chaff. Historically, animals like oxen or horses were walked in circles over the wheat to achieve the same result more efficiently.
Cleaning the Threshed Grain
After threshing, the resulting mixture contains grain kernels along with lighter debris, including chaff, dust, and straw fragments. The next step, called winnowing, separates the grain from this lighter material by exploiting the difference in density. The heavier kernels fall almost straight down, while the lighter chaff is carried away by an air current.
One of the oldest winnowing methods involves using natural wind by slowly tossing the threshed mixture into the air from a basket or tray. The wind catches the lighter chaff and blows it a short distance away, while the grain falls back down onto a collection surface. A more controlled approach uses an artificial air current, such as a box fan.
To use a fan, the threshed mixture is slowly poured from one container into a second, with the fan positioned to blow horizontally across the falling stream. The fan speed must be carefully regulated, as a setting that is too high can blow away the grain itself. For a cleaner result, the material can first be passed through a coarse sieve to remove the largest pieces of straw, and then through a finer screen to eliminate dust before the final air separation.