It is well established that the properties of cast metals are greatly improved by refinement of their grain size. The method employed in this study for the refinement of grain size of commercially pure aluminum and zinc castings is inoculation of naphthalene in powder form to the mould prior to pouring the molten metal. The results show that the
addition of naphthalene remarkably suppresses the formation of columnar grains and refines the structure. Increasing the amount of naphthalene addition also minimizes and may eliminate the formation of the shrinkage cavity. Furthermore, the ability of castings
for mechanical working increases as the naphthalene addition increases