Pyrex is the brand name of borosilicate glass. It was first introduced by Corning Glass Works in 1924.

Pyrex was created by adding boron to the traditional glassmaker's "frit" of silicate sand, soda, and ground lime. The boron gave this new borosilicate glass a reduced thermal coefficient (about one-third that of ordinary glass), making it more resistant to heat. Pyrex is also lighter in weight. Since Pyrex melts at a higher temperature than ordinary glass, some new techniques were required to bring Pyrex into industrial production. Borrowing from the welding trade, new burners combining oxygen with natural gas were required.

Caltech's famous 200-inch telescope mirror at Mount Palomar was cast by Corning during 1934-36 out of Pyrex, which expands and contracts less than ordinary glass.

Unexpectedly, Pyrex and the new "lampworking" techniques generated a cottage industry in quickly-produced glass novelties that quickly degenerated into kitsch.

External links

• Illustrated history of the Palomar observatory and the Pyrex lens (http://www.astro.caltech.edu/observatories/palomar/history/)
• Robert A Mickelson, "History of Art Glass Lampworking" (http://www.enclopedia.netnz.com/glass/lampwork.html)

Reference

• Rogove, Susan Tobier; Steinhauer, Marcia Buan (1993). Pyrex by Corning: A Collector's Guide. Antique Publications. ISBN 091541094X

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