Vertical crucible pulling method for producing a glass body having a high silicic-acid component

A method for producing a glass body with high silicic-acid content, said method comprising:

• supplying SiO2 granules from above into an elongated, substantially cylindrical crucible,
• heating the SiO2 granules to a softening temperature, so that a softened glass mass comprising a melt surface is formed,
• drawing off the softened glass mass via a bottom opening of the crucible so as to form a glass strand, and
• cutting the glass strand to a length to obtain the glass body,
• wherein the supplying of the SiO2 granules causes a bulk heap to be formed that partly covers the melt surface while leaving a melt edge not covered by said bulk heap, and
• the method further comprising
• optically detecting the melt surface,
• wherein during the optical detecting of the melt surface a width of at least a sub-section of the melt edge is determined consecutively and is set to a value within a target width range by setting a supply rate of the SiO2 granules;
• and
• wherein the width of the melt edge is set to a value within the target width range by a nominal supply rate of SiO2 granules based on a throughput of the drawn-off glass mass, and wherein the nominal supply rate is changed by not more than 10%.