Method and apparatus for producing a glass component

A method of producing a glass component, comprising:

• preparing a void-containing intermediate product that contains doped or non-doped SiO2;
• introducing the intermediate product into a sheath tube composed of glass, which has a longitudinal axis and an inner bore;
• and
• thermal treating the intermediate product in the sheath tube,
• wherein a first gas-permeable gas diffuser is inserted into the sheath tube's inner bore, which first gas-permeable gas diffuser is displaceable along the sheath tube's longitudinal axis and is pressed against the intermediate product during the thermal treatment,
• wherein a compression force is generated by means of a clamping device, which exerts a pressure on the first gas diffuser, and
• wherein the clamping device comprises an elastically deformable spring element inserted in the sheath tube's inner bore, or a slide which is displaceable in the sheath tube's inner bore and having a first magnetic element composed of a magnetic material and a second magnetic element which is movable in the direction of the longitudinal axis outside the sheath tube's inner bore and which acts on the magnetic element.