Gristmill

Gristmill with water wheel, Skyline Drive, Virginia, 1938

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

History

Ancient Near East

According to historian Helaine Selin, there is evidence indicating that the corn mill originated from the Persian Empire before 350 BC, likely in what are today Iran or Iraq, originally for the purpose of grinding corn. There were quarries known for their millstones in Iran and on the upper Tigris in what is today Turkey. The mills invented at this date had horizontal, propeller-like water wheels that drove the millstones directly.

There was an expansion of grist-milling in the Byzantine Empire and Sassanid Persia from the 3rd century AD onwards, and then the widespread expansion of large-scale factory milling installations across the Islamic world from the 8th century onwards.

Ancient China

Manually operated mills utilizing a crank-and-connecting rod were used in the Western Han dynasty (202 BC – 9 AD).

Medieval Islamic world

The first geared gristmills were invented by Muslim inventors in the medieval Islamic world, and were used for grinding corn and other seeds to produce meals, and many other industrial uses such as fulling cloth, husking rice, papermaking, pulping sugarcane, and crushing metalic ores before extraction. Gristmills in the Islamic world were often made from both watermills and windmills. In order to adapt water wheels for gristmilling purposes, cams were used for raising and releasing trip hammers to fall on a material. The first wind-powered gristmills driven by windmills were built in what are now Afghanistan, Pakistan and Iran in the 9th and 10th centuries.

Medieval Europe

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.

Britain and North America

Classical mill designs are usually water powered, though some are wind mills, or powered by livestock. A sluice gate is used to open a channel and so start the water flowing and a water wheel turning. In most such mills 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 also 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 10 rpm, or so.

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 going 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 grain is lifted in sacks onto the sack floor at the top of the mill. The sacks are emptied into bins, where the grain falls down through a hopper to the stones on the stone floor below. The flow of grain is regulated by shaking it along 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 it gets fed down a chute to be collected in sacks on the ground or meal floor. A very similar process is used for grains such as wheat, kamut, etc to make flour as well as 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 he patented and promoted a fully automated mill design.

The Boykin Mill, in Boykin, South Carolina, has an operating grist mill where meal and grits have been ground by water power the same way for over 150 years.

Modern mills

Historically, gristmills contained rotating stones powered by water or by wind; later mills used steam engines for power, and modern mills typically use electricity or fossil fuels to spin heavy steel rollers. These techniques produce visibly different results, but can be made to produce nutritionally and functionally equivalent output.

Gristmills only grind clean grains, that is, grain from which stalks and chaff have previously been removed, but some mills also housed equipment for threshing, sorting, and cleaning prior to grinding. Gristmills also grind corn into meal.

Modern mills are almost certainly "merchant mills", that is, they are privately owned and accept money or trade for milling grains, or the corporations that own the mills buy unmilled grain and then own the flour produced. Early mills were almost always built and supported by farming communities and typically a percentage of each farmer's grain called a "miller's toll" was set aside for the miller in lieu of wages. Although gristmill can refer to any mill that grinds grain, the term historically was used to refer to a local mill where farmers brought their own grain and received the flour from it, minus the "miller's toll." Modern mills use serrated and flat cast iron 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 wheat or graham flour.

List of historic gristmills

Canada

Notable functioning gristmills

• Kings Landing Historical Settlement, New Brunswick, Canada
• Morningstar Mill, St. Catharines, Canada

United States

Notable functioning gristmills

• Glade Creek Grist Mill in Babcock State Park, West Virginia
• Jenney Grist Mill, Plymouth, Massachusetts
• Kymulga Mill, Childersburg, Alabama
• Grist Mill at Old Sturbridge Village, Sturbridge, Massachusetts
• West Point Mill, Durham, North Carolina
• Mingus Mill, Sevier County, Tennessee
• Cooper Mill, Chester, New Jersey
• Newlin Grist Mill, Glen Mills, Pennsylvania
• War Eagle Mill, Rogers, Arkansas
• Stony Brook Grist Mill, Stony Brook, New York
• Carpenter's Grist Mill, Perryville, RI
• Old Mill at Berry College, Rome, GA
• Dexter Grist Mill, Sandwich, Massachusetts

Ruins, remnants, partially preserved)

• Audra State Park, West Virginia
• Causey's Mill, Virginia
• Mill Ruins Park, Minneapolis, Minnesota
• Valley Falls State Park, West Virginia

United Kingdom

Main article: Watermills in the United Kingdom

Sweden

• Eldkvarn, Stockholm

See also

• Grist
• Water mill
• Windmill
• Tide mill
• Water wheel
• Textile mill

External links

• Historic Mill Information and Images
• The Society for Preservation of Old Mills
• Old Stone Mill National Historic Site of Canada
• Stockdale Mill
• Greenbank Mill
• Gristmill diagram and description
• North American Millers' Association — How Wheat Flour is Milled
• Worlds Grits Festival St. George, SC
• Site of first grist mill in North America, 1607
• Prewetts Mill A British mill built in 1861 driven by steam until the 1970s
• Working Mill in Pickwick, Minnesota, 1854
• Cooper Mill - Working Grist Mill in Chester, New Jersey 1826
• Newlin Grist Mill - Only Working Grist Mill in Pennsylvania
• War Eagle Mill - A Working Water Powered Grist Mill in Rogers, Arkansas