Abstract: A glass has a coefficient of thermal expansion in a temperature range from 20° C. to 300° C. of 4.5 ppm/K or less, and a T4 temperature, defined as the temperature at which the glass has a viscosity of 104 dPa*s, at 1500° C. or more, and having a reboil propensity score of less than 10 measured in a reboil propensity test. The reboil propensity score is determined as a number of bubbles per glass rod formed from the glass after the reboil propensity test.

Abstract: A glass has a coefficient of thermal expansion in a temperature range from 20° C. to 300° C. of 4.5 ppm/K or less, and a T4 temperature, defined as the temperature at which the glass has a viscosity of 104 dPa*s, at 1500° C. or more, and having a reboil propensity score of less than 10 measured in a reboil propensity test. The reboil propensity score is determined as a number of bubbles per glass rod formed from the glass after the reboil propensity test.

Abstract: A glass rod includes: a glass including a glass composition, 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) and (b) a largest semi-major axis length Imajor(n), normalized by the average semi-major axis length lmajor(a); 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 that has the largest semi-major axis length Imajor(n) and (d) an average value of the cross-sectional areas, normalized by an average value of the cross-sectional areas; wherein the quality index (tlvmajor+lav) is 0.090 or less.