The Quern Stones (aka Mill Stones)
Outwood Mill has a couple of different types of Quern Stones.
Quern-stones have been used throughout the world to grind materials, the most important of which was usually grain to make flour for bread-making. They were generally replaced by millstones once mechanised forms of milling appeared, particularly the water mill and the windmill, although animals were also used to operate the millstones. However, in many non-Westernised, non-mechanised cultures they are still manufactured and used regularly and have only been replaced in many parts of the world in the last century or so.
In early Maya civilizations the process of nixtamalization was distinctive in that hard, ripe kernels of maize (corn) were boiled in water and lime, thus producing nixtamal which was then made into unleavened dough for flat cakes by grinding with a handstone on a quern
As well as grain, ethnographic evidence and Mesopotamian texts shows that a wide range of foodstuffs and inorganic materials were processed using stone querns or mortars, including nuts, seeds, fruit, vegetables, herbs, spices, meat, bark, pigments, temper and clay. Moreover, one study analysing quern-stones noted that a number of querns had traces of arsenic and bismuth, unlike their source rocks, and had levels of antimony which were ten times higher than those of the rocks. The authors concluded that this was probably due to the use of these querns in the preparation of medicines, cosmetics, dyes or even in the manufacture of alloys.
Querns were widely used in grinding metals ores after mining extraction. The aim was to liberate fine ore particles which could then be separated by washing for example, prior to smelting. They were thus widely used in gold mining in antiquity.
In the Shetlands tobacco wasn’t smoked at first, but ground up into snuff, and inhaled up the nose. Snuff-querns consisted of an upper and lower stone, fixed together by a central iron pivot. The quern was held on the users lap, the eye was filled with dried tobacco leaves and then the upper-stone was turned using the handle. The friction caused by the turning ground the leaves into a fine powder that built up around the edge of the lower-stone. Many snuff-querns had a small hole or cut made near the edge of the upper-stone, into which a pointed end of a lamb’s horn was placed in order to turn the stone; an alternative to using a handle.
Rotary hand quern
As the name implies, the rotary quern used circular motions to grind the material, meaning both the quern and the handstone were generally circular. The handstone of a rotary quern is much heavier than that of saddle quern and provides the necessary weight for the grinding of unmalted grain into flour. In some cases the grinding surfaces of the stones fit into each other, the upper stone being slightly concave and the lower one convex.
This rotary hand quern being used in India around the 1930’s is almost identical to the one located in the roundhouse of Outwood Mill.
As you can see from the image the hand quern in Outwood Mill sits atop a full size Millstone made from Derbyshire Peak Stone.
Millstones or mill stones are used in windmills and watermills, including tide mills, for grinding wheat or other grains.
The type of stone most suitable for making millstones is a siliceous rock called buhrstone (or burrstone), an open-textured, porous but tough, fine-grained sandstone, or a silicified, fossiliferous limestone. In some sandstones, the cement is calcareous.
Outwood Mill has FOUR Millstones within it set into two pairs. This means that Outwood Mill is rerferred to as a “Two Stone” mill (Two Pairs). The front pair of stones are made from Derbyshire Peak Stone and the rear pair are made from Buhrstone.
Types Of Millstone
Millstones used in Britain were commonly of two types:
Millstone with furrows
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 burr stones, 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.
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.
The Runner Stone
A runner stone is the upper of a pair of working millstones. 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.
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 furrows and lands are arranged in repeating patterns called harps. A typical millstone will have six, eight or ten harps. The grooves provide a cutting edge and help to channel the ground flour out from the stones. When in regular use stones need to be dressed periodically, that is, re-cut to keep the cutting surfaces sharp.
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 is supported by a cross-shaped metal piece (rind/rynd) fixed to a “mace head” topping the main shaft or spindle leading to the driving mechanism of the mill (either water or wind powered). 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.
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.
In the image above you can just see the edge of the millstone through the glass of the stone vat in Outwood Mill. This is the rear stones and therefore this is the set made from buhrstone.
The stones were encased in wood (called Vats) to stop all the fine powder billowing through the mill and also to help minimize the risk of a stone fire spreading as lining the vat with zinc was a good fire break.
Sources Include: http:www.wikikpedia.org