The formation of stearate on precipitated calcium carbonate (PCC) has been examined. The object of coating the filler surface is to achieve improved mechanical properties in the resulting composite material. The coating of a filler with stearate allows the modification of the energies of interaction. so as to improve dispersion and alter the mechanical properties of the interphase region. In this work, Fourier transform infra-red spectroscopy (FTIR) has been used to characterise the efficiency of stearate formation. X-ray photoelectron spectroscopy (XPS) has been used to estimate the thickness of the stearate coating on the surface of the filler. By using dynamic mechanical analysis (DMTA), a variation in mechanical properties has been demonstrated.