Abstract: The invention relates to an apparatus and a method for low-contamination melting of high-purity, aggressive and/or high-melting glass or glass-ceramic. According to the invention, for this purpose a melt is heated in a crucible or melting skull crucible by means of high-frequency radiation and is mixed or homogenized in the melting crucible. It is preferable for a gas nozzle, from which gas bubbles, e.g. oxygen bubbles (known as O2 bubbling), escape into the melt, to be provided at the base of the crucible. This alone makes it possible to achieve surprising multiple benefits in the melting skull crucible. Firstly, unmelted batch which drops into the melt in solid form, for example from above, is melted down more quickly as a result of more intensive mixing with the liquid fraction of the melt, secondly the temperature distribution in the melt is made more even, thirdly a uniform distribution or mixing of different glass constituents is achieved, and fourthly the redox state of the glass can be adjusted.

Abstract: A method and an apparatus for heating a melt in a melting vessel with cooled walls is provided. The melt is heated conductively by current flowing between at least two cooled electrodes, which each replace part of the wall of the melting vessel.

Abstract: 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.

Abstract: An apparatus and a method for low-contamination melting of high-purity, aggressive and/or high-melting glass or glass-ceramic are provided. For this purpose, a melt is heated in a crucible or melting skull crucible by means of high-frequency radiation and is mixed or homogenized in the melting crucible. A gas nozzle, from which gas bubbles, e.g. oxygen bubbles (known as O2 bubbling), escape into the melt, is provided at the base of the crucible.

Abstract: A device for the melting of highly pure optical glasses and/or for the treatment of melts is provided. The device is intended for a subsequent refining or homogenization process making use of the skull technique. The device uses a number of coated metal tubes whose surface is free of glass-coloring ions.