There is additional information in the Glass Art Society Journal 1997, pp. 27-30, and 77-80, as well as in the vertical file: Telescopes--Specific--Univ. of Arizona.
This video shows the process at Steward Observatory Mirror Laboratory to produce the world's largest telescope mirrors. To make the honeycomb mirrors, chunks of borosilicate glass are melted (cast) in a complex mold, and spun into shape in a specially designed rotating oven (also called a spinning furnace). The technique is also referred to as spin casting. These honeycomb mirrors are called "Angel Mirrors" after professor Roger Angel who designed them. Smaller mirrors have already been made for Mount Hopkins (Arizona), for Kitt Peak (Arizona), for the Magellan Project in Chile. Also included are a brief film clip of making the 200" disk.
The brief glass related footage includes placing the boroslicate chunks in the mold, melting and spinning, with time lapse photography of the melting, and the moving of the mirror out of the furnace, followed by polishing.
Since the video focuses on the plans for the 8.4 meter tandem mirrors for Mount Graham, Arizona, the first of which was cast in January 1997, the video may have been made in 1996.