An optimum amount of deflocculant was determined for three-component suspensions, based on a mixture design approach. Three raw materials were used, characterized as clay, feldspar and quartz. Ten compositions were prepared using the mixture design approach. Deflocculation curves were measured for suspensions with 40 wt.% of solids, adding sodium silicate as dispersant. The optimum deflocculant amount (ODA) was determined for each suspension, corresponding to the lowest value of apparent viscosity considering two nearest experimental points. It was observed that ODA increases linearly with the increase of the clay fraction in the mixture. A response surface and polynomial regression could be used to identify the composition range that satisfies usual conditions in wet ceramics processing.