The sugar cane crystallisation process is currently performed through three stages. The efficiency of the third stage, named C crystallisation, is of high interest because it is the ultimate step of transforming saccharose in liquid form into crystals. In most of industries, the control of C crystallisation is performed following an electrical conductivity setpoint of the sucrose solution. However, this measurement presents several disadvantages which can damage the process control. In order to perform an efficient supervision of C crystallisation in Bois Rouge sugar mill, we have equipped the pan with two different brix sensors. Due to their costs, these measurements are seldom used in sugar industry. This work does show the benefits using these measurements to observe the process advancement of several crystallisation during the 2003 campaign.