In 1929, Corning Glass Works accepted a commission to make a 200-inch Pyrex disk for use in a reflecting telescope on Mount Palomar in California. After several trial castings of smaller disks, Corning poured a 200-inch disk in 1934. When part of the mold broke loose, the disk was ruined, but it was annealed (cooled slowly) as an experiment to gather information necessary for a second, successful casting later that year. This is the initial disk, which has been displayed at the Museum since it opened. This video features Rob Cassetti, senior director, creative services and marketing at The Corning Museum of Glass.