The Mirror Lab casting team unpacks and inspects a shipment of glass to be used to make the giant telescope mirrors. Over 20 tons of glass pieces will be placed into the mirror mold, one piece at a time. The glass is called E6 borosilicate and is specially manufactured by Ohara Glass in Japan, using sand from the gulf coast of Florida. In its chemical composition, the glass is similar to Pyrex used in cookware. Randy Lutz, Mirror Lab casting team manager, carefully inspects each piece of glass using polarized light to evaluate internal stresses and check for imperfections. (Photo credit: Ray Bertram, U of Arizona)

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