“…This defect is formed when the surface of the liquid metal folds upon itself during turbulent pouring, and a volume of air is trapped between the two unwetted sides of the oxide films that come into contact with each other. This defect, which was not recognised for many years due to its extremely small thickness, has nowadays grabbed the attention of many researchers, who have studied its formation, 1-3 influence on mechanical properties of solidified casting, 4-6 behaviour in liquid metals, [7][8][9] healing mechanism in different alloys [10][11][12][13][14] and elimination from the melt. 15,16 The role of double oxide film defects in the formation of hydrogen pores in aluminium castings was first suggested by Campbell, 1 who calculated the pressure required for homogeneous nucleation of an H bubble in liquid Al melt to be extremely high (i.e.…”