In order, inter alia, to provide an apparatus and a process for melting inorganic substances which allow a high product quality to be obtained and the technological outlay to be reduced, the invention provides a process and an apparatus in which the volumetric ratios between a melting region and a refining region can be flexibly adapted. The process comprises the steps of adding a batch into at least one first region (12) on the feed side (10) of a scull crucible (1), heating the crucible contents (30), melting down the crucible contents (30) in the at least one first region (12) of the scull crucible (1), entry into at least one second region (22) on the discharge side (20) of the scull crucible (1), melting down and/or refining the crucible contents (30) in the at least one second region (22) of the scull crucible (1), and removing the melted-down crucible contents through at least one removal apparatus (25), with the volume on the feed side (10) and/or the discharge side (20) of the scull crucible (1) being set variably.