The porosity defects on high castability aluminum alloy like Al-Si alloys was investigated but in the low castability aluminum alloys like Al-Cu alloy had been rarely conducted. However, low fluidity of Al-Cu alloys became enthused material in the future. Gas porosity characterization studies are useful for quality improvement of Al-Cu alloy. The paper aims to explore about gas porosity formation with the addition of copper in the casting process to reduce porosity defects. The experimental object melted aluminum ingot and copper together at clay bowl on reveberatory furnace. The copper added by weight analysis and the optical emission spectrometry was the measure of weight percentage of element in duralumin. Identification of the morphology and quantity of gas porosity at the cut surface of casting duralumin was done by using scanning electron and optic microscopy, and pycnometry and planemetry. The experimental results showed the gas porosity dimensionally, while the non-dimensionally caused  by hydrogen gas. Gas porosity in Al-Cu alloys hypoeutectic increased with the increasing copper content. Gas porosity to be ordered or round shape which depends on high or low copper content, respectively.

porosity, castability, characterization, solidification, pycnometry.