Sacks of grain, delivered by road or river, were hoisted into the mill by the sack hoist through the two projecting gables known as lucams.

The grain was cleaned and stored and then channelled by gravity through all the stages of grinding and processing to be bagged as flour at the bottom of the mill.

Grain was stored in huge bins on this floor before it was poured down through small rectangular chute holes to the Stone floor.

The fall of the grain
The grain was first fed into the hopper, then to the shoe, and from there into the eye of the running stone. The shoe was vibrated by the metal damsel attached to the revolving runner stone. The angle of the shoe was controlled by a string called the crook string. This regulated the amount of grain that fell into the centre of the stones.

The grain was then spread by centrifugal force between the running stone and the stationary bed stone, grinding as it went. The flour then fell down a chute to the floor below.

As the flour fell it was collected in sacks positioned at the bottom of the chute. Once full the sacks were attached to an internal sack hoist and lifted back up to the Stone floor where the flour was sifted on a wire machine to separate off the bran or outer skin. The graded flour was then brushed down the chutes to be re-bagged as a finished product.

Even the whitest and finest stone milled flour, obtained by sifting the flour through the wire machine over and over again, had fine branny particles and yellow flecks of wheatgerm. Today, flour is often bleached artificially to make it white. The flour produced at Houghton is 100% stoneground wholewheat and is ground from wheat grown at the National Trust's Wimpole Home Farm, Cambridgeshire.

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Millstone ventilation system
The most unusual feature of Houghton Mill was a unique millstone ventilation system introduced by Potto Brown. This system was the subject of a lengthy court case in 1858-9, in which the miller William Christie, was accused of stealing George Hinton Bovill's design for a ventilation system.

Potto acted as an expert witness for Christie, only to find himself defending his own system from accusations of infringment of copyright. He successfully argued his case, by demonstrating that his system was based on a French model which predated Bovill's invention.

The ventilation system was designed to improve both the performance and the output of the millstones by drawing the moisture from the flour and the dust produced during grinding off into a separate room where it was then expelled outside.

The trunking to which the millstone cases were connected is still in place just above floor level on both sides of the stone floor. We do not know where the dust room was originally positioned but one of the fans, recently found in the loft, is on display.

A pair of millstones comprises the bed stone and the upper or runner stone. When milling, the runner stone revolves around 125 times a minute. The two main types of millstone are French burr stone, a form of freshwater quartz, and grit stone from the Derbyshire peak district.

The stones would become so worn from grinding that they had to be dismantled and sharpened, or dressed, every twelve working days. Arthur Chopping is shown here dressing the stones in 1915. Ropes to lift the stones were hung from rings still visible on the beams above.