more resistant to physical damage when dropped, which is believed to be the most common cause of breakage in glass bakeware. The glass is also cheaper to produce and more environmentally friendly. However, its thermal shock resistance is lower than borosilicate's, leading to potential breakage from heat stress if used contrary to recommendations. Since the closure of the soda-lime plant in England in 2007, European Pyrex has been made solely from borosilicate. The differences between Pyrex-branded glass products has also led to controversy regarding safety issuesin 2008, the U.S. Consumer Product Safety Commission reported it had received 66 complaints by users reporting that their Pyrex glassware had shattered over the prior ten years yet concluded that Pyrex glass bakeware does not present a safety concern. The consumer affairs magazine Consumer Reports investigated the issue and released test results, in January 2011, confirming that borosilicate glass bakeware was less susceptible to thermal shock breakage than tempered soda lime bakeware. However, they admitted their testing conditions were "contrary to instructions" provided by the manufacturer. STATS analyzed the data available and found that the most common way that users were injured by glassware was via mechanical breakage, being hit or dropped, and that "the change to soda lime represents a greater net safety benefit." Use in telescopes Because of its low expansion characteristics, Pyrex borosilicate glass is often the material of choice for reflective optics in astronomy applications. In 1932, George Ellery Hale approached Corning with the challenge of fabricating the telescope mirror for the California Institute of Technology's Palomar Observatory project. A previous effort to fabricate the optic from fused quartz had failed, with the cast blank having voids. The mirror was cast by Corning during 1934–1936 out of borosilicate glass. After a year of cooling, during which it was almost lost to a flood, the blank was completed in 1935. The first blank now resides in the Corning Museum of Glass. See also Jena glass References Sources Gantz, Carroll, (2001). DESIGN CHRONICLES: Significant Mass-produced Products of the 20th Century, Schiffer Publishing, External links Official Pyrex website Vintage Pyrex Reference Guide Glass trademarks and brands Kitchenware brands Low-expansion glass Transparent materials Products introduced in 1915 American brands Boron compounds Corning Inc. Kitchenware it:Vetro borosilicato