The Boulter is a large automated sieve that is used to refine the flour. It is situated against the wall nearest Horspath on the Stone Floor.
It consists of wooden frame in which an angled drum of stretched cloth rotates powered by the mill. The milled flour is fed in at the top of the drum and the flour is spun out through three different thickness' of cloth leaving the bran to be collected at the base of the drum. These three different qualities of refined flour are then collected in sacks beneath the machine. In effect the Boulter operates in much the same way as a spin dryer.
Wheatley Mill's Boulter still exists but at present is in poor condition. It is intended to restore it to be fully functioning in the future.