In many cases, the hydrocyclone control is desirable for efficient separation especially in case of changing feed conditions. Control concept based on exact mathematical models is not satisfactory due to the complexity of the physical process. In this case, fuzzy control is a suitable solution. The data are primarily derived from an optical sensor that monitors the outside view of the free underflow stream (spray angle). A throttling valve, serving as an actuator, is installed around the overflow pipe that regulates the volume split of the cyclone. This work presents a fuzzy hydrocyclone control to stabilize the separation, as a result of varying feed conditions in kaolin processing. The aim is to control the final product size (kaolin) and then to replace the multi-stages hydrocyclones which are currently used with only one stage fuzzy controlled hydrocyclone separation process to produce high quality kaolin in the overflow product even with changing the feed conditions during the separation. The results showed that sharp separations are performed with a spray angle in the range of 25° to 35°. Therefore, in that application, the control is focused on stabilization of the spray angle. A controlled spray angle of 26° was found to give optimum results concerning the kaolin quality separated in the overflow. The improved operation characteristics present new options for extensive applications of fuzzy hydrocyclone control.