World Library  
Flag as Inappropriate
Email this Article

Millstone

Article Id: WHEBN0000167364
Reproduction Date:

Title: Millstone  
Author: World Heritage Encyclopedia
Language: English
Subject: Watermill, Quern-stone, Meeten's Mill, West Chiltington, Clayton Windmills, Lower Mill, Woodchurch
Collection: Food Grinding Tools, Grinding and Lapping, Heraldic Charges, Stone Objects
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Millstone

The basic anatomy of a millstone. Note that this is a runner stone; a bedstone would not have the "Spanish Cross" into which the supporting millrynd fits.

Millstones or mill stones are stones used in grist mills, for grinding wheat or other grains.

Millstones come in pairs. The base or bedstone is stationary. Above the bedstone is the turning runner stone which actually does the grinding. The runner stone spins above the stationary bedstone creating the "scissoring" or grinding action of the stones. A runner stone is generally slightly concave, while the bedstone is slightly convex. This helps to channel the ground flour to the outer edges of the stones where it can be gathered up.

The runner stone is supported by a cross-shaped metal piece (rind or rynd) fixed to a "mace head" topping the main shaft or spindle leading to the driving mechanism of the mill (wind, water (including tide) or other means).

Contents

  • History 1
  • Material 2
  • Patterning 3
  • Grinding with millstones 4
  • Heraldry 5
  • See also 6
  • References 7
  • External links 8

History

Millstone factory site in Britain

Neolithic and Upper Paleolithic people used millstones to grind grains, nuts, rhizomes and other vegetable food products for consumption.[1] These implements are often called grinding stones. They used either staddle stones or rotary querns turned by hand. Such devices were also used to grind pigments and metal ores prior to smelting.

In India, grinding stones (Chakki) were used to grind grains and spices. These consist of a stationary stone cylinder upon which a smaller stone cylinder rotates. Smaller ones, for household use, were operated by two people. Larger ones, for community or commercial use, used livestock to rotate the upper cylinder.

Material

Buhr stone with resurfacing instructions

The type of stone most suitable for making millstones is a siliceous rock called burrstone (or buhrstone), an open-textured, porous but tough, fine-grained sandstone, or a silicified, fossiliferous limestone. In some sandstones, the cement is calcareous.[2]

Millstones used in Britain were commonly of two types:

  • Derbyshire Peak stones of grey Millstone Grit, cut from one piece, used for grinding barley; imitation Derbyshire Peak stones are used as decorative signposts at the boundaries of the Peak District National Park. Derbyshire Peak stones wear quickly and are typically used to grind animal feed since they leave stone powder in the flour, making it undesirable for human consumption.
  • French burrstones, used for finer grinding. Not cut from one piece, but built up from sections of quartz, cemented together with plaster, and bound with iron bands. French Burr comes from the Marne Valley in northern France.

In Europe, a third type of millstone was used. These were uncommon in Britain, but not unknown.

  • Cullen stones (stones from Cologne) were quarried in the Rhine Valley near Cologne, Germany.[3]

Patterning

Dressing a millstone

The surface of a millstone is divided by deep grooves called furrows into separate flat areas called lands. Spreading away from the furrows are smaller grooves called feathering or cracking. The grooves provide a cutting edge and help to channel the ground flour out from the stones.

The furrows and lands are arranged in repeating patterns called harps. A typical millstone will have six, eight or ten harps. The pattern of harps is repeated on the face of each stone, when they are laid face to face the patterns mesh in a kind of "scissoring" motion creating the cutting or grinding function of the stones. When in regular use stones need to be dressed periodically, that is, re-cut to keep the cutting surfaces sharp.

Millstones need to be evenly balanced, and achieving the correct separation of the stones is crucial to producing good quality flour. The experienced miller will be able to adjust their separation very accurately.

Grinding with millstones

A pair of millstones in Holgate Windmill
1.Hopper 2.Shoe 3.Crook string 4.Shoe handle 5.Damsel 6.Eye 7.Runner stone 8.Bedstone 9.Rind 10.Mace 11.Stone spindle 12.Millstone support 13.Wooden beam 14.Casing (Tentering gear not shown)

Grain is fed by gravity from the hopper into the feed-shoe. The shoe is agitated by a shoe handle running against an agitator (damsel) on the stone spindle, the shaft powering the runner stone. This mechanism regulates the feed of grain to the millstones by making the feed dependent on the speed of the runner stone. From the feed shoe the grain falls through the eye, the central hole, of the runner stone and is taken between the runner and the bed stone to be ground. The flour exits from between the stones from the side. The stone casing prevents the flour from falling on the floor, instead it is taken to the meal spout from where it can be bagged or processed further.

Gilingang bato (ancient rice millstone, Minalin, Pampanga, Philippines)

The runner stone is supported by the rind, a cross-shaped metal piece, on the spindle. The spindle is carried by the tentering gear, a set of beams forming a lever system with which the runner stone can be lifted or lowered slightly and the gap between the stones adjusted. The weight of the runner stone is significant (up to 1500 kg) and it is this weight combined with the cutting action from the porous stone and the patterning that causes the milling process.

Millstones for some water powered mills (such as Peirce Mill) spin at about 125 rpm.[4]

Especially in the case of wind powered mills the turning speed can be irregular. Higher speed means more grain is fed to the stones by the feed-shoe and grain exits the stones quicker because of their faster turning speed. The miller has to reduce the gap between the stones so more weight of the runner presses down on the grain and the grinding action is increased to prevent the grain being ground too coarsely. It has the added benefit of increasing the load on the mill and so slowing it down. In the reverse case the miller may have to raise the runner stone if the grain is milled too thoroughly making it unsuitable for baking. In any case the stones should never touch during milling as this would cause them to wear down rapidly. The process of lowering and raising the runner stone is called tentering and lightering. In many windmills it is automated by adding a centrifugal governor to the tentering gear. Depending on the type of grain to be milled and the power available the miller may adjust the feed of grain to stones beforehand by changing the amount of agitation of the feed-shoe or adjusting the size of the hopper outlet. Milling by millstones is a one-step process in contradiction with roller mills in modern mass production where milling takes place in many steps. It produces wholemeal flour which can be turned into white flour by sifting to remove the bran.

Heraldry

A millstone in the arms of Höör, Sweden

As an old item and symbol for industry, the millstone also has found its place as a charge in heraldry.

See also

References

  1. ^
  2. ^
  3. ^
  4. ^ NPS publication "Peirce Mill" GPO: 2004--304-337/00145 Reprint 2004

External links

  • Millstone Dressing Tools
  • European millstone quarries: a database
  • Abandoned Millstones - Peak District
  • Video clip demonstrating millstone dressing
  • Millstones & Querns on Flickr
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.