In the case of some special castings, even the minimal gas bubbles are not permitted. The vacuum induction melting and casting conducted under the vacuum is the most radical technique for production of such gas-free metals. Many of the complex alloys and superalloys, such as the titanium and nickel-based alloys used in aerospace industry are reactive with atmospheric oxygen or nitrogen. Melting these alloys in the vacuum limits the formation of the non-metallic oxide and nitride inclusions in the metal. Furthermore, dissolved gases are extracted from melt through the influence of reduced pressure on gas–metal equilibria. The solubility of gases in the melt increases with temperature; in solid metals, it is much lower than in the melt. The released gases therefore escape from the melt during solidification, or, partly remaining in the metal, may form gas bubbles. By decreasing the partial pressure of a particular gas above the melt, the equilibrium amount of the dissolved gas in the alloy is also reduced. This principle is utilized in a way of reducing the pressure (vacuumizing) in the space above the melting unit and in the casting space in order to substantially reduce the gas solubility in the melt, and thereby reduce the risk of the gas bubbles incidence in the casting. The vacuum molten alloys are normally poured into the investment moulds which are positioned within the vacuum melt chamber or the adjacent evacuated vessel.