Calcium stearate undergoes a partial melting to a mesomorphic state at about 100 °C, as shown by discontinuities in the density–temperature relation and in differential cooling measurements, and by the onset of plasticity. No surface activity is exhibited by the soap in mineral oil, even in the mesomorphic state. Calcium stearate dispersions in a non-polar mineral oil are essentially lyophobic up to 180 °C, whereas the soap is dispersed to a sol in more polar oils at a temperature slightly above the partial melting point.The viscosity of these dispersions, measured over a range of temperatures in a variable-pressure efflux viscosimeter shows unusual characteristics. A maximum viscosity at intermediate temperatures was found, accompanied by a high degree of dilatancy. The presence of water is shown to lower the viscosity and destroy dilatancy by agglomeration of the dispersed soap.