The quality of breast prostheses dependant on homogeneous mixing of materials during the manufacturing process. This research endeavoured to investigate the mixing of two silicones that are widely used in the production of breast prostheses. The effect of impeller design on obtaining a homogeneous mixture was investigated. Four different types of impellers were used to investigate the effect of stirrer type, diameter, speed, position and time to obtain a homogeneous mixture. Stirring speeds of 500 rpm, 800 rpm and 1100 rpm were investigated together with stirring height and stirring diameter. Percentage of homogeneity of the mixture was investigated ranging from 10 to 60 minutes with a 10 minutes interval. The effect of stirring time and speed on viscosity was also examined. It was found that a four blade radial impeller gives the best result for mixing in all cases.