It has been reported about interaction mechanism between aluminium alloys and aluminosilicate refractories in aluminium foundry industry. The mechanism is concluded in formation a porous film on the refractory surface, non protected from further interaction between refractory components and aluminium, magnesium owing to reaction with negative bulk effects with ensuring metal penetration in refractory material through permeable interstices. It has been defined, that critical sizes of interstices for penetration of aluminium melt in refractory in relation to oscillation of metal level and displacement of three-phase boundary “metal-gas-refractory” are changed within interval of 20–40 μm with unwetting agents and within interval of 10–30 μm during degeneration of additives or their deficiency.