Using experimental samples of type-KI quartz glass processed in a barostatic chamber as an example, it is demonstrated that bubbles can be removed from it virtually completely. An investigation of the quality indices (birefringence, fine-grain inhomogeneity, and refractive index) recorded that they showed substantial variations after each operation, from the time that the glass was fabricated from quartz until the final product was obtained after the barostatic chamber, hot pressing, and rough annealing. However, the indices returned to their initial values at the completion of the processing cycle.
V. S. Doladugina and V. N. Stepanchuk, "The effect of barostat processing on the characteristics of type-KI quartz glass," J. Opt. Technol. 70, 204-209 (2003)