The validation of each simulation code used in foundry domain requires individual approach due to its specificity. This validation can by
elaborated on the basis of experimental results or in particular cases by comparison the simulation results from different codes. The article
concerns the influence of grey cast iron density curve and different forms of solid fraction curve Fs=f(T) on the formation of shrinkage
discontinuities. Solid fraction curves applying Newtonian Thermal Analysis (NTA) were estimated. The experimental and numerical
simulation tests were performed on the castings, which were made with Derivative Thermal Analysis (DerTA) standard cups. The
numerical tests were realized using NovaFlow&Solid (NF&S), ProCast and Vulcan codes. In this work, the coupled influence of both
curves on the dynamics of the shrinkage-expansion phenomena and on shrinkage defects prognosis in grey cast iron castings has been
revealed. The final evaluation of the simulation systems usefulness should be based on validation experiment, preceded by comparing the
simulation results of available systems which are proposed in given technology.