After brick clay is loaded into the extruder, a vacuum serves to remove the air, thus preventing the formation of air pockets and the subsequent breakage of bricks. Similar to brick clay, ceramic clay is first placed in a mixer and pressurized with water or water vapour to form a homogeneous mixture. It is then transferred to an extruder where it is pressed into moulds under high pressure. The material is then extruded to the proper length, dried and fired.