Kneaders are used to produce highly viscous paint concentrates, uncured rubber compositions, and putties. Double arm kneader consists of two z-shaped blades rotating horizontally in opposite directions in a container with a divided trough or saddle. The blades can be overlapped or run at different speeds. Materials to be kneaded or worked is dropped into the trough and mixed for 5 to 20 minutes. Sometimes the mass is heated while in the machine but commonly it is cooled to remove the heat generated during the mixing action. The trough is often unloaded by tilting it so that its contents spill out.