240 pages, spiral bound. . The Wolfgang mills use a unique grinding stone made by the Hawo Corp, also from Germany. The details of these stones may be of interest to our customers. Right into the 19th Century, sandstone, granite, or quartz were the common, locally available stones used in wind and water mills. The invention by the Frenchman Sorel of the cement that bears his name, enabled him to produce artificially hardened millstones by adding the very hard mineral corundum.
Natural stones are usually soft and smooth.
Artificially roughening the surface has no substantial influence. Stones made of corundum, bound in magnesia cement, are hard, but are susceptible to the presence of foreign bodies in the grinder. Hawo has taken this type of composite and developed it further. Under high pressure the mass is pressed into the millstone mould and fired at very high temperatures. After firing, Hawo's extremely hard special stone is first made exactly level during which its surface is roughened.