A gristmill (also: grist mill, corn mill or flour mill) grinds grain into flour. The term can refer to both the grinding mechanism and the building that holds it.

The Greek geographer Strabo reports in his Geography of a water-powered grain-mill to the Mithradates VI Eupator at Cabira, Minor Asia, before 71 BC. The early mills had horizontal paddle wheels, which was known as “Norse wheel”, as many were found in Scandinavia. The paddle wheel was attached to a shaft which was in turn, attached to the center of the millstone called the “runner stone”. The turning force produced by the water on the paddles was directly on the runner stone, causing it to grind against a stationary “bed”, a stone of a similar size and shape. This simple arrangement has not been necessary, but had the disadvantage that the speed of rotation was only suitable for use in mountainous regions with fast-flowing streams. This dependence on the speed of rotation is highly variable and the optimum growth rate is not maintained. Vertical wheels were used in the Roman Empire by the end of the first century BC, and these were described by Vitruvius. The peak of Roman technology is likely to have a 19-meter waterfall, giving an estimated 2.4 tonnes to 3.2 tons per hour. Water mills seem to remain in use during the post-Roman period, and by 1000 AD, mills in Europe were rarely more than a few miles apart. In England, the Domesday Survey of 1086 gives a precise count of England’s water-powered flour mills: there were 5,624, or about one for every 300 inhabitants, and this was probably typical throughout western and southern Europe. From this time onward, water wheels began to be used for other than grist milling. In England, the number of mills in operation followed growth population, and peaked at around 17,000 by 1300. Limited extant examples of gristmills can be found in Europe from the High Middle Ages. An extant well-preserved waterwheel and gristmill on the Ebro River in Spain is associated with the Real Monasterio de Nuestra Senora de Rueda, built by the Cistercian Monks in 1202. The Cistercians were known for their use of this technology in Western Europe in the period 1100 to 1350. Geared gristmills were also built in the medieval Near East and North Africa, which were used for grinding grain and other seeds to produce meals. Gristmills in the Islamic world were powered by both water and wind. The first wind-powered gristmills were built in the 9th and 10th centuries in Afghanistan, Pakistan and Iran.

Although the terms “gristmill” or “millet” may refer to that grinds grain, the terms were used historically for a millet toll. ” Early mills were almost always built and supported by farming communities and the miller’s toll in lieu of wages. Most towns and villages had their own mill so that local farmers could easily transport their grain there to be milled. These communities have been relied on as a staple part of the diet. Classical mill designs are usually water-powered, though some are powered by the wind or by livestock. In a watermill a sluice gate is open to allow water to flow onto, or under, to make it turn. In most watermills the water wheel was mounted vertically, ie, edge-on, in the water, but in some cases horizontally (the tub wheel and so-called Norse wheel). Later designs incorporated horizontal steel or cast iron turbines and these were sometimes refitted into the old wheel mills. In most wheel-driven mills, a large gear-wheel called the wheel drive is mounted on the same axle as the wheel drive and this drives to a smaller gear-wheel, the wallower, one has main driveshaft running vertically from the bottom to the top of the building. This system of gearing ensures that the main shaft turns faster than the water wheel, which typically rotates around 10 rpm. The millstones themselves turn at around 120 rpm. They are ugly one on the other. The bottom stone, called the bed, is fixed to the floor, while the top stone, the runner, is mounted on a separate spindle, driven by the main shaft. A wheel called the stone nut connects the spindle to the main shaft, and it can be moved to the turning shaft, turning the shaft to the other. This might include a mechanical sieve to refine the flour, or a wooden drum to wind up a chain used to hoist sacks of grain to the top of the mill house. The distance between the stones can be varied to produce the grade of flour required; moving the stones closer together produces finer flour. The grain is lifted in the sacks on the floor at the top of the mill on the hoist. The sacks are then emptied into bins, where the grain falls down through a hopper to the millstones on the stone floor below. The flow of grain is regulated by shaking it in a gentle sloping trough (the slipper) from which it falls into a hole in the center of the runner stone. The milled grain is collected by the grooves in the runner stone of the stones and is fed to the market. A similar process is used for making flour, and for making corn. In order to prevent the vibrations of the machinery of the building of the building apart, a gristmill will be at least two separate foundations. American inventor Oliver Evans revolutionized this labor-intensive process at the end of the eighteenth century when he patented and promoted a fully automated mill design.

Modern mills typically use fossil fuel fuels to spin heavy steel, or cast iron, serrated and flat rollers to separate the bran and germ from the endosperm. The endosperm is ground to create white flour, which can be recombined with the bran and germ to create whole grain or graham flour. The different milling techniques produce visibly different results, but can be made to produce nutritionally and functionally equivalent output. Stone-ground flour is, however, preferred by many bakers and natural food advocates because of its texture, nutty flavor, and the belief that it is more nutritionally superior and has a better baking quality than steel-roller-milled flour. It is asked that, as the stones grow slowly, The wheat germ is not exposed to the fate of excessive temperatures that would cause the fat to germinate and become rancid, which would destroy some of the vitamin content. Stone-milled flour, especially when milled from hard wheat. Gristmills only grind “clean” grains from which stalks and chaff have previously been removed, but historically some of them have been removed, sorting, and cleaning prior to grinding. Modern mills are usually “merchant mills” that are either privately owned and accepted for the purpose of milling grain, or they are owned by corporations that buy unmilled grain and then own the flour produced. Stone-milled flour, especially when milled from hard wheat. Gristmills only grind “clean” grains from which stalks and chaff have previously been removed, but historically some of them have been removed, sorting, and cleaning prior to grinding. Modern mills are usually “merchant mills” that are either privately owned and accepted for the purpose of milling grain, or they are owned by corporations that buy unmilled grain and then own the flour produced. Stone-milled flour, especially when milled from hard wheat. Gristmills only grind “clean” grains from which stalks and chaff have previously been removed, but historically some of them have been removed, sorting, and cleaning prior to grinding. Modern mills are usually “merchant mills” that are either privately owned and accepted for the purpose of milling grain, or they are owned by corporations that buy unmilled grain and then own the flour produced. sorting, and cleaning prior to grinding. Modern mills are usually “merchant mills” that are either privately owned and accepted for the purpose of milling grain, or they are owned by corporations that buy unmilled grain and then own the flour produced. sorting, and cleaning prior to grinding. Modern mills are usually “merchant mills” that are either privately owned and accepted for the purpose of milling grain, or they are owned by corporations that buy unmilled grain and then own the flour produced.

One common pest in flour is the Mediterranean flour moth. Moth larvae produce a web-like material that clogs machinery.

* Robert L. Burns, Consolidated Flour Mills of Kansas