A process for manufacturing of castings from an essentially liquid reactive medium as casting material which, above its gelation temperature, reacts to form a solid material, in which process the medium is fed from a supply tank (1), in which the temperature of the casting material lies substantially below its gelation temperature, to a casting mould (5) of which the temperature lies above the gelation temperature of the casting material, characterized in that the casting material is substantially preheated directly before it enters the casting mould (5) to a temperature close to but below the gelation temperature of the casting material so that it is still in a state suitable to be fed into the casting mould (5).