After each reduction rollermill, the ground material goes to a sifter that removes the flour produced by that rollermill and sends the larger-size middlings to another set of reduction rollermills. It requires 13 or more separate reduction grinding and sifting operations before the middlings are reduced to flour. Each of the flours produced in the breaking and reduction process has a distinctive quality and property. The miller can blend these flour streams together to produce a myriad of different flours. It is also possible to produce several types of blended flours simultaneously from one type of cereal grain.
Further versatility is gained by milling grain with varying protein content.
Depending on the amount of grain milled each day, each of the described operations may require multiple machines to handle the load. Therefore, the flourmill may consist of many rollermills, sifters, and purifiers. The mill building will usually consist of several floors. The various materials are lifted from the bottom floor to the top through tubes with a stream of air. After reaching the top floor, gravity passes the material through a series of sifters, purifiers, and rollermills and is then relifted by air.