Glass rod, set of glass rods, and process for the production of a glass rod

A glass rod, comprising:

• a glass including a glass composition,
• wherein the glass rod includes a length lrod, which is from 100 mm to 1600 mm;
• wherein the glass rod includes an average semi-major axis length lmajor(a), within a respective cross-section of the glass rod a semi-major axis length lmajor(n) is a distance from a center-of-mass of the cross-section to a furthest boundary of the glass rod within the cross-section;
• wherein the glass rod includes an average semi-minor axis length lminor(a), within a respective cross-section of the glass rod a semi-minor axis length lminor(n) is a distance from the center-of-mass of the cross-section to a nearest boundary of the glass rod within the cross-section;
• wherein the glass rod includes the glass composition having a T4 temperature-defined as a temperature at which the glass has a viscosity of 104 dPa·s—of at least 1400° C.;
• wherein the glass rod has a total relative length variation of a semi-major axis tlvmajor, a relative local area variation lay, and a quality index defined as a sum of tlvmajor+lav;
• wherein the total relative length variation of the semi-major axis tlvmajor is determined as an absolute difference between (a) a smallest semi-major axis length Imajor(n) of 50 equidistant cross-section positions of the glass rod and (b) a largest semi-major axis length Imajor(n) of the 50 equidistant cross-section positions, normalized by the average semi-major axis length lmajor(a) of the 50 equidistant cross-section positions;
• wherein the 50 equidistant cross-sections are positioned along the length lrod of the glass rod, starting at a position of 0.01*lrod as a first position and employing a plurality of additive increments of 0.02*lrod for each subsequent position;
• wherein the relative local area variation lav is determined as an absolute difference between (c) a cross-sectional area at a respective one of the 50 equidistant cross-section positions that has the largest semi-major axis length Imajor(n) of the 50 equidistant cross-section positions and (d) an average value of a plurality of cross-sectional areas of the 50 equidistant cross-section positions, normalized by an average value of a plurality of cross-sectional areas of the 50 equidistant cross-section positions;
• wherein the quality index is 0.090 or less.