What are the honeycomb mirrors made of?
The mirror substrates are made of glass. Glass is used because it is a very stable material. As long as you don’t drop it, a piece of glass will maintain its shape for thousands of years. Glass can also be polished to a very smooth and precise surface without any granular structure. The spun-cast mirror blanks produced at the Mirror Lab are made from E6 low expansion borosilicate glass produced by the Ohara Corporation in Japan. The coefficient of thermal expansion (CTE) of E6 glass is 2.8 x 10-6/C. Ohara makes this glass in large clay pots, each holding more than a ton. Ohara supplies shipments of glass to the Mirror Lab in pieces typically weighing ~ 4-5 kg. • What makes the glass reflective? After the glass surface is polished to a very precise figure, it is turned into a front-surface mirror by applying a very thin metallic coating. The function of the glass substrate is to hold the shape of this thin metal layer which reflects the light. Aluminum is most frequently used, although
