Heatherslaw Mill How does the Mill work?
Heatherslaw Corn Mill is actually two water mills under one roof, each with its separate water wheel and mill race. Each mill has three pairs of horizontal grinding stones and a vertical stone for pearl barley polishing.
The power comes in from the undershot water wheel at the bottom of the building and is transmitted by gears and shafts to the top.
The grain arrives in sacks at ground level and is then moved by hoist to the top floor. This is where the Miller stands, with the controls of the sluice gate (to vary the amount of water pushing the wheel around), the gap between the millstones and the flow of grain all within easy reach. This is a difficult job as mishandling the millstones could cause sparks that would make the dust explode! The Miller also has to set the Timing Clock to judge how long to polish the barley, which depends on quality, moisture content and the condition of the millstones.
The grain is then tipped into hoppers that bring it down to the millstones. Two of the pairs of millstones you can see are made of French Burr, one of the hardest natural stones. These are used to mill wheat. The others are made of Derbyshire Peak gritstone, for shelling oats. The lower stones of a pair (bedstones) do not move – it is the top (runner) stone that revolves. The meal is then dropped down a chute and bagged. Pearl barley is tipped into a separate hopper that takes it into a vertical millstone arrangement with a vertical stone and outer casing rotating at different speeds to husk and polish it. It then goes through a dresser, is milled and dressed again and then bagged.
The Upper Mill has been fully restored to working order and produces about seven tons of flour a year. The Lower Mill remains much as it was before the restoration and is used to demonstrate parts of the milling process that usually take place out of sight.