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Allied Mills flour mill on the banks of the Manchester Ship Canal

A gristmill or grist mill is a building in which grain is ground into flour, or the grinding mechanism itself. In many countries these are referred to as corn mills or flour mills.

Contents

History

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Early history

The old water mill at Decew Falls, Niagara Escarpment, St.Catharines, Canada

The first water powered gristmills in Europe were probably built toward the end of the first century BC. The first written account is that of Strabo, describing the mill at Cabira, although the chronology and design of the mill are ambiguous.

At Cabira, the palace of Mithradites was built, and the water-mill, the animal park, the hunting grounds close by, and the mines. - Strabo

Although it is usually assumed the mill was built during Mithradates reign there is no real evidence of this and it could have been built any time during the 1st century.[1] It is also not known whether Strabo saw the mill himself or was told about it.[1]

Grinding mechanism in an old Swedish flour mill

The early mills had horizontal paddle wheels, an arrangement which later became known as the "Norse wheel", as many were found in Scandinavia.[2] The paddle wheel was attached to a shaft which was, in turn, attached to the centre of the millstone called the "running stone". The turning force produced by the water on the paddles was transferred directly to the running stone, causing it to grind against a stationary "bed", a stone of a similar size and shape.[2] This simple arrangement required no gears but had the disadvantage that the speed of rotation of the stone was dependent on the volume and flow of water available and was, therefore, only suitable for use in mountainous regions with fast-flowing streams.[2] This dependence on the volume and speed of flow of the water also meant that the speed of rotation of the stone was highly variable and the optimum grinding speed could not always be maintained.[2]

Vertical wheels were in use in the Roman Empire by the end of the first century BC, and these were described by Vitruvius.[1] The peak of Roman technology is probably the Barbegal aqueduct and mill where water with a 19-meter fall drove sixteen water wheels, giving a grinding capacity estimated at 2.4 to 3.2 tonnes per hour. Water mills seem to have remained 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 purposes other than grist milling. In England, the number of mills in operation followed population growth, and peaked around 17,000 by 1300.[3]

The first geared gristmills[4] were built by Muslim inventors in the medieval Islamic world, and were used for grinding grain and other seeds to produce meals. They also had many other industrial uses such as fulling cloth, husking rice, papermaking, pulping sugarcane, and crushing metallic ores before extraction. Gristmills in the Islamic world were powered by both water and wind. In order to adapt water wheels for gristmilling purposes, cams were used for raising and releasing trip hammers to fall on a material.[5] The first wind-powered gristmills were built in in the 9th and 10th centuries in what are now Afghanistan, Pakistan and Iran.[6]

Limited 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.

Classical British and American mills

Stretton Watermill, 17th-century built operational mill in Cheshire, England

Although the terms "gristmill" or "corn mill" can refer to any mill that grinds grain, the terms were used historically for a local mill where farmers brought their own grain and received back ground meal or flour, minus a percentage called the "miller's toll."[7] Early mills were almost always built and supported by farming communities and the miller received the "miller's toll" in lieu of wages. Most towns and villages had their own mill so that local farmers could either easily transport their grain there to be milled. These communities were dependent on their local mill as bread was 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 opened to allow water to flow onto, or under, a water wheel to make it turn. In most watermills the water wheel was mounted vertically, i.e., 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 pit wheel is mounted on the same axle as the water wheel and this drives a smaller gear-wheel, the wallower, on a 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 at around 10 rpm.

The millstones themselves turn at around 120 rpm. They are laid one on top of 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 runner's spindle to the main shaft, and this can be moved out of the way to disconnect the stone and stop it turning, leaving the main shaft turning to drive other machinery. This might include driving a mechanical sieve to refine the flour, or turning 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 sacks onto the sack 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 gently sloping trough (the slipper) from which it falls into a hole in the center of the runner stone. The milled grain (flour) is collected as it emerges through the grooves in the runner stone from the outer rim of the stones and is fed down a chute to be collected in sacks on the ground or meal floor. A similar process is used for grains such as wheat to make flour, and for maize to make corn meal.

In order to prevent the vibrations of the mill machinery from shaking the building apart, a gristmill will often have 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

Modern mills typically use electricity or fossil 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 may 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 flavour, and the belief that it is nutritionally superior and has a better baking quality than steel-roller-milled flour.[8] It is claimed that, as the stones grind relatively slowly, the wheat germ is not exposed to the sort of excessive temperatures that could cause the fat from the germ portion to oxidize and become rancid, which would destroy some of the vitamin content.[8] Stone-milled flour has been found to be relatively high in thiamin, compared to roller-milled flour, especially when milled from hard wheat.[8]

Gristmills only grind "clean" grains from which stalks and chaff have previously been removed, but historically some mills also housed equipment for threshing, sorting, and cleaning prior to grinding.

Modern mills are usually "merchant mills" that are either, privately owned and accept money or trade for milling grains or, are owned by corporations that buy unmilled grain and then own the flour produced.

Functioning historic gristmills

Canada

United States

United Kingdom

References

  1. ^ a b c Oleson, John Peter (30 Jun 1984). Greek and Roman mechanical water-lifting devices: the history of a technology. Springer. pp. 373. ISBN 9027716935. http://www.amazon.co.uk/Greek-Roman-Mechanical-Water-lifting-Devices/dp/9027716935/ref=sr_1_1?ie=UTF8&s=books&qid=1260878169&sr=1-1. Retrieved 15 December 2009. 
  2. ^ a b c d Denny, Mark (4 May 2007). "Waterwheels and Windmills". Ingenium: five machines that changed the world. The Johns Hopkins University Press. pp. 36-38. ISBN 0801885868. http://books.google.co.uk/books?id=OlGoFBIb-GEC&pg=PA36&lpg=PA36&dq=norse+wheel&source=bl&ots=aj9LdOgfZJ&sig=djvlescVJ37VWf-USWZT_sFi58U&hl=en&ei=XYQnS-lDgYDhBtO5haQN&sa=X&oi=book_result&ct=result&resnum=8&ved=0CBwQ6AEwBw#v=onepage&q=norse%20wheel&f=false. Retrieved 15 December 2009. 
  3. ^ Gimpel, J., The Medieval Machine, Gollanz, 1976, Chapter 1.
  4. ^ Donald Routledge Hill (1996), "Engineering", p. 781, in (Rashed & Morelon 1996, pp. 751-95)
  5. ^ Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64-69 (cf. Donald Routledge Hill, Mechanical Engineering)
  6. ^ Adam Lucas (2006), Wind, Water, Work: Ancient and Medieval Milling Technology, p. 65, Brill Publishers, ISBN 9004146490
  7. ^ "ARTFL Project: Webster Dictionary, 1913". The University of Chicago - Department of Romance Languages and Literature. http://machaut.uchicago.edu/cgi-bin/WEBSTER.sh?WORD=gristmill. Retrieved 2006-09-28. 
  8. ^ a b c Campbell, Judy; Mechtild Hauser, Stuart Hill, (1991). "NUTRITIONAL CHARACTERISTICS of ORGANIC, FRESHLY STONE-GROUND, SOURDOUGH & - CONVENTIONAL BREADS". Ecological Agriculture Projects Publications. Ecological Agriculture Projects. http://www.soilandhealth.org/06clipfile/Nutritional%20charateristics%20of%20organic%20freshly%20stone%20-%20ground.htm. Retrieved 15 December 2009. 

Further reading

  • Richard Bennett & John Elton. History of corn milling (London, Simpkin, Marshall and company, 1898).

See also

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