The principle of casting is to melt a pure metal or an alloy of several metals and then pour the liquid material into a mould. The glowing melt is transported into a refractory steel ladle and the caster must then withstand temperatures of up to 2,552°F (1,400°C). The melting temperature is specific to each metal used. The melting temperature of cast iron varies from 2,075°F (1,135°C) to 2,552°F (1,400°C), depending on its carbon and silicon content. Zinc alloys, on the other hand, melt at 420°C, aluminium alloys at around 1,292°F (700°C) and copper at 2,282°F (1,250°C).