Source of Aluminum Casting Porosity: Dissolved Hydrogen in Melt Molten aluminum readily absorbs hydrogen generated from moisture in the surrounding environment. Hydrogen solubility in solid aluminum is much lower than in the liquid state. During solidification, dissolved hydrogen precipitates into bubbles and forms porosity defects inside finished castings. On continuous melting and casting lines of 25–35 t/h, raw material variation and ambient humidity fluctuations lead to