The stalwarts of the Hallaton Field Work Group have been out and about over the last few weeks, in all weathers, searching for a deserted village in the Welland Valley. Imagine our surprise then when we came across three wedge shape pieces of rock lying together. Upon closer examination it became clear that they formed half of a millstone. Well more accurately, half of the upper millstone called the runner stone. The photograph shows our runner stone face up, with the grooves cut into it; when in operation it would of course be face down. It also shows three stones and the full millstone would have been made up of six segments. Our stones measure on average 12” long x 5-14” width of wedge x 5-7” depth (in inches) with variations. The centre hole is 9½” diameter.
Most millstones in the East Midlands are of Derbyshire gritstone, but these are marble or quatrz in appearance. English millstones are of one piece, so why is this one made up of six segments. Pete Wilford quickly recognised them as being of French origin. The best and most popular stone ever discovered for grinding wheat into white flour is the French Burr. This stone is a freshwater quartz and was quarried at La Ferte sous Jouarre near the town of Chalons in the Marne Valley in Northern France, the stone from this district became world famous. The remarkable thing about this stone from La Ferte sous Jouarre was that it was only found in small pieces ranging from about 12 to 18 inches long, from 6 to 10 inches wide, by 5 to 10 inches thick, usually embedded in layers of clay. There were sometimes pieces of a larger size, but none large enough to make a complete millstone of the usual size 4 feet to 4 feet, 6 inches diameter, so that the French millstone of popular size, had to be built up. One reason why French stones were so successful was their high percentage of porosity. Some pieces were simply a mass of porous cells and as the stones wore away, new cutting edges appeared which could be worked without being refaced or redressed. Other pieces of La Ferte sous Jouarre stone were extremely hard and of close texture. The more porous pieces of stone were often light brown in colour and called “nutmeg” burrs. The hard, close textured pieces were usually of lighter colour and called “white” burrs. French stones produced a whiter flour from wheat because the extremely hard nature of the stone was far less abrasive than any other stone used. An abrasive stone tends to shred the outer part of the grain of wheat, the bran, into a powder. This fine powdered bran dresses through the fine mesh silk or woven wire of the flour dressing machinery or bolters together with the white part of the wheat meal and the flour thus produced is of a darker colour.
In the heyday of millstone milling, there were hundreds of firms of millstone makers, and these people imported vast quantities of the La Ferte sous Jouarre blocks of stone into their respective countries. The process of building the complete millstones from the blocks of rough stones, begins with selecting suitable pieces so as to form, usually two concentric rings looking rather like keystones of an arch. The number of sectional pieces used, varies, depending on the size of the blocks; some French millstones have as many as nineteen sections, while there are others with as few as four sections. Where there are two rings of stone sections, a good millstone maker will select the harder burrs for the outer ring and the softer burrs for the inner ring. This selection of stone is to allow for the extra wear on the outer ring as, of course, the periphery of the runner stone travels much faster than the centre and also covers a larger area of grain or material contact. Apart from this obvious consideration, the area round the centre of the stone, the eye, has to be slightly farther apart than the outer edge of the stones to allow the grain to enter between the stones. This “dishing” of the stones was also known to some millers as “bosoming.” The sections of the stone are trimmed and dressed so as to be a good fit and form a perfectly round, solid millstone.
The runner stone has a round hole in the centre, usually about 10 inches diameter to form the eye, through which the grain is fed. The bed stone is built with a square hole in the centre about 10 inches across, this is to accommodate the neck bearing of the driving or balancing spindle. The pieces of stone are cemented or plastered together and bound with iron bands to prevent bursting when the millstones are in use. These bands are usually “sweated” or shrunk on, this is to say, that the iron bands are heated to a red hot condition and thus expand. In this red hot condition the bands are driven over the edge of the stones and as the bands cool they contract to become extremely tight. The top of the runner stone is usually finished off with a layer of plaster of Paris, which is sometimes mixed with small pieces of stone and smoothed off to form a slightly convex top. When new, a French runner stone of 4 feet to 4 feet, 6 inches diameter is usually about 12 to 15 inches thick at the circumference, which is known as the “skirt” of millstones, and 15 to 18 inches thick at the eye or centre. The weight of these runner stones is upwards of 2,400 pounds.
With thanks to Charles Howell for his expertise and notes on these stones.