Like the electric current which we unconcernedly snap on and off for light, heat, food, entertainment and a host of other services, we often lose sight of the marvel of a material which we use each day- portland cement. Just how is the "magic powder made? Although the refinements in manufacture have been all-encompassing, the basic processes are the same. Portland cement is composed of lime and silica with small quantities of such materials as gypsum, iron oxide and aluminum. The basic materials are combined chemically under extremely high temperatures and ground to a fine powder. Small quantities of materials are added at various stages of manufacture to control setting time, facilitate grinding, entrain air and to achieve other purposes. Cement manufacture begins with a explosion of the basic rock which is later crushed. At this point the initial blending of basic ingredients takes place. The ingredients are then finely grinded at placed in a kiln to dry. When the ingredients are dried and heated to a molten mass. The resulting product is called clinker pellets. They are then reground into a powder.