Pouring the 200 inch disk at Corning Glass Works

In 1928, the famed astronomer, George Ellery Hale, had a vision. He wanted to build the world’s largest telescope at Palomar Mountain in California—a research instrument that would allow scientists to view the skies as never before. The creation of the largest single piece of glass ever made was entrusted by Hale in 1929 to Corning Glass Works using their signature Pyrex®, a special glass designed to resist heat expansion. George V. McCauley, a Corning physicist and engineer, set about achieving what engineers at other companies had failed to do: casting a 200-inch mirror blank. In March 1934, Corning poured a 200-inch disk, but part of the mold broke loose during the pouring, ruining the blank. McCauley decided to continue with annealing (a process required to slowly cool the glass) as an experiment. That imperfect disk has become an iconic object in the collection of The Corning Museum of Glass. It has been suspended in the same spot for 60 years, since the Museum opened to the public in 1951. The second attempt at pouring was successful, and after a year’s annealing time, the disk was finished and taken by train to California. The disk was finally installed in 1948 in the Palomar Observatory, where it remained the world’s largest effective telescope until 1993, aiding in the discovery of quasars and the first known brown dwarf star. The telescope is still in use.