Definição e significado de Pyrex

  A Pyrex measuring cup manufactured circa 1980, featuring graduations in both metric and U.S. Customary systems.

Pyrex (trademarked as PYREX) is a brand which was introduced by Corning Incorporated in 1915 for a line of clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware.

Corning no longer manufactures or markets Pyrex-branded borosilicate glass kitchenware and bakeware in the United States, but Pyrex borosilicate products are still manufactured under license by various companies. World Kitchen, LLC, which was spun off from Corning in 1998, licensed the Pyrex brand for their own line of kitchenware products—differentiated by their use of clear tempered soda-lime glass instead of borosilicate.

  History

Borosilicate glass was first made by the German chemist and glass technologist Otto Schott, founder of Schott AG in 1893, 22 years before Corning produced the Pyrex brand. Schott AG sold the product under the name "Duran."

In 1908, Eugene Sullivan, Director of Research at Corning Glass Works, developed Nonex, a borosilicate low-expansion glass, to reduce breakage in shock-resistant lantern globes and battery jars. Sullivan had learned about Schott's borosilicate glass as a doctoral student in Leipzig, Germany. Jesse Littleton of Corning discovered the cooking potential of borosilicate glass by giving his wife a casserole dish made from a cut-down Nonex battery jar. Corning removed the lead from Nonex, and developed it as a consumer product.^[1] Pyrex made its public debut in 1915 during World War I, positioned as an American-produced alternative to Duran.

A Corning executive gave the following account of the etymology of the name "Pyrex":

The word PYREX is probably a purely arbitrary word which was devised in 1915 as a trade-mark for products manufactured and sold by Corning Glass Works. While some people have thought that it was made up from the Greek pyr and the Latin rex we have always taken the position that no graduate of Harvard would be guilty of such a classical hybrid. Actually, we had a number of prior trade-marks ending in the letters ex. One of the first commercial products to be sold under the new mark was a pie plate and in the interests of euphonism the letter r was inserted between pie and ex and the whole thing condensed to PYREX.^[2]

In the late 1930's and 1940's, Corning also introduced other products under the Pyrex brand, including opaque tempered soda-lime glass for bowls and bakeware, and a line of Pyrex Flameware for stovetop use; this borosilicate glass had a bluish tint caused by the addition of alumino-sulfate. ^[3][4] In 1958 an internal design department was started by John B. Ward. He redesigned the Pyrex ovenware and Flameware. Over the years designers such as Penny Sparke, Betty Baugh, Smart Design, TEAMS Design, and others have contributed to the design of the line.

Corning divested its consumer products division in 1998, forming the company World Kitchen, LLC. Corning discontinued its production of Pyrex products, but still licensed the Pyrex brand to other companies, including World Kitchen, and Newell Cookware Europe^[5] France-based cookware maker Arc International acquired Newell's European business in early 2006.^[6], and currently owns rights to the brand in Europe, the Middle East and Africa.^[7][8]

  Composition

  A clear tempered Pyrex soda-lime glass measuring cup with a blueish color produced by World Kitchen, and a clear borosilicate glass Pyrex measuring cup produced by Corning (right)

Older clear-glass Pyrex manufactured by Corning before 1998, Arc International's Pyrex products, and Pyrex laboratory glassware is made of borosilicate glass. According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 14% boron, 51% oxygen, .3% sodium, 1% aluminium, 38% silicon, and less than 1% potassium.^[9][10]

According to glass supplier Pulles and Hannique, borosilicate Pyrex is made of Corning 7740 glass, and is equivalent in formulation to Schott Glass 8830 glass sold under the "Duran" brand name.^[11] The composition of both Corning 7740 and Schott 8830 is given as 80.6% SiO₂, 12.6% B₂O₃, 4.2% Na₂O, 2.2% Al₂O₃, 0.04% Fe₂O₃, 0.1% CaO, 0.05% MgO, and 0.1% Cl.

Pyrex glass cookware manufactured by World Kitchen is made of tempered soda-lime glass instead of borosilicate.^[12] World Kitchen justified this change by stating that soda-lima glass was cheaper to produce, is the most common form of glass used in bakeware in the United States, and that it also had higher mechanical strength than borosilicate—making it more resistant to breakage when dropped, which it believed to be the most common cause of breakage in glass bakeware. However, unlike borosilicate, it is not as heat resistant, leading to an increase in breakage from heat stress.^[5][13][14]

The differences between Pyrex products depending on manufacturer has also led to safety issues—in 2010, the Consumer Product Safety Commission received several complaints by users reporting that their Pyrex glassware had shattered at high temperatures. The consumer affairs magazine Consumer Reports investigated into the matter after obtaining copies of the complaints, determining that the complainants had in fact been using World Kitchen-produced Pyrex products, and had incorrectly assumed that they would have the same characteristics and strength as their borosilicate counterparts.^[15]

  Usage in telescopes

Because of its low expansion characteristics, Pyrex borosilicate glass is often the material of choice for reflective optics in astronomy applications. The California Institute of Technology's 200-inch (5.1 m) telescope mirror at Palomar Observatory was cast by Corning during 1934–1936 out of borosilicate glass.^[16]

In 1932, George Ellery Hale approached Corning with the challenge of fabricating the required optic for his Palomar project. A previous effort to fabricate the optic from fused quartz had failed.

Corning's first attempt was a failure, the cast blank having voids. Using lessons learned, Corning was successful in the casting of the second blank. After a year of cooling, during which it was almost lost to a flood, in 1935 the blank was completed. The first blank now resides in Corning's Museum of Glass.

  Footnotes

  References

• Rogove, ST; Steinhauer, MB (1992). Pyrex by Corning: A Collector's Guide. Crystal Publications. ISBN [[Special:BookSources/0-911410-94-X|0-911410-94-X]]. 
• Gantz, Carroll, (2001). DESIGN CHRONICLES: Significant Mass-produced Products of the 20th Century, Schiffer Publishing, ISBN 978-0-7643-2323-5

  External links

• Pyrex official website
• Vintage Pyrex Reference Guide