In electroslag remelting (ESR), the material cast into electrodes is successively melted in a slag bath, refined by various chemical and physical mechanisms and solidified in a water-cooled copper mould. In addition to a significantly improved degree of purity, controlled solidification can also be achieved. Compared to ingot casting, the low melt volume and the induced stirring result in a reduction of macrosegregation and, due to the low local solidification rates, a reduction of microsegregation. At the contact surface between the slag and the mould, a slag skin about 1-3 mm thick is formed, which on the one hand reduces the direct heat loss to the mould, but on the other hand also reduces the cooling speed of the metal.