The glass actually fails in tension. It just splits down the middle. This is shown in Fig 6. The glass tends to split in a ying-yang pattern. The lenses were glued in place with some marvelous glue.
Nothing seems to attack it, and it stands high temperature.
I picture the laser factory as being in one wing of a plant where they manufacture supersonic aircraft. When they needed glue, they just went over into the next bay and got a pot of the same stuff used to glue the wings on the supersonic aircraft. We had to try to rescue the lenses as we expected colder temperatures on a mountain than in my garage. This reverses the problem. Instead of crunching the glass, the cell wants to pull away from it.