How to Make the Worlds Largest Mirrors.If these large mirrors were made of solid glass they could not be cooled evenly enough to relieve stress and would be too heavy to move.
The Mirror Lab creates a mirror with a honey comb structure. This reduces the weight, but maintains the mirrors rigidity. The honey comb structure also allows the mirror to be cooled evenly over three months, eliminating stress in the glass.
Alumina-Silica cores are used to create the honey comb structure of the finished mirror.
After placing the cores in the mold, they are topped with foot ball size chunks of glass covering the entire surface.
The electric furnace that heats the very high quality optical glass from Japan to 1100 degrees fahrenheit. The glass reaches the consistency of honey and flows around the cores. What an electric bill that must be.
A mirror after cooling for three months in the furnace. The temperature was slowly lowered so all the glass cools at the same rate. This relieves stress that would cause the mirror to crack.
This mirror was ground to the correct parabolic shape and is now being polished. Laser beams are bounced of the surface checking the shape of the surface. A computer uses this information to guide that little red polishing machine to the spots that need polishing. The mirror is polished to a tolerance of less than 20 nanometers.