Patent ID: 8596094

Claim:
A method of making a silica glass having a uniform fictive temperature, the method comprising the steps of: a. providing the silica glass, the silica glass having a strain point T s , a fictive temperature T f , and a relaxation rate at the fictive temperature T f , wherein the silica glass has a hydroxyl concentration that varies by at least 0.5 ppm; and b. annealing the silica glass, wherein annealing the silica glass comprises: i. heating the silica glass to a first temperature that is greater than target fictive temperature T f,t , cooling the glass to a second temperature that is less than the target fictive temperature T f,t and greater than T s -40° C., and heating the silica glass from the second temperature to the target fictive temperature T f,t , at a progressively decreasing heating rate that is less than a rate of change of the fictive temperature T f for a time sufficient for the fictive temperature T f of the silica glass to come within 3° C. of the target fictive temperature T f,t ; and ii. cooling the silica glass from the target fictive temperature T f,t to a temperature below the strain point T s at a cooling rate that is greater than the relaxation rate of the glass at the target fictive temperature T f,t , wherein the silica glass has a fictive temperature T f that varies by less than 3° C. after the annealing step.