Abstract: An aluminum melt is processed by the injection of a sparging gas through a spinning nozzle into the melt in a preheat, conditioning and processing step sequence, with a predetermined proportion of hydrogen being employed with the sparging gas during the processing step to assure that the hydrogen content of the melt is such that the density of the solidified product is within a desired range on a repeatable basis. The conditioning step is employed to facilitate the attaining of the desired result on such repeatable basis in an advantageous manner such as to minimize the processing time and the amount of the hydrogen/sparging gas mixture necessary for the desired density control.