The present study was performed on Al–Si–Cu 319 alloy castings obtained from cooling fin sand molds with variable fin size design. The amount of melt hydrogen, Sr, and Ti was also varied. In total 32 alloys were prepared to give 132 alloy/melt/solidification conditions. Porosity measurements were carried out on samples prepared from these castings using an optical microscope-image analysis system. It was found that at low solidification times, pore nucleation takes place predominantly in intergranular regions. The pore morphology is mostly elongated, the pores being observed to lie along the grain boundaries (due to the long freezing range of the alloy). The probability of pore nucleation taking place in interdendritic regions increases at higher solidification times, and the pore morphology tends to be more rounded, as well. Melt hydrogen levels of ~0.3 ml/100 g produce extremely large pores in the casting, even at high solidification rates. Thus, in order to produce sound castings, it is important that the melt be properly degassed in order to keep the hydrogen level at the minimum possible. Proper preheating of the sand mold is essential to ensure against the occurrence of reaction porosity along the casting surface.