Pyrex

Background

Pyrex glass is a borosilicate glass first produced by The Corning Glass Works company. It is made by heating raw materials like silica sand and boric oxide to extremely high temperatures for extended periods of time. The molten material is then processed into different types of glassware. First formulated during the early twentieth century, Pyrex has become an important material for a variety of applications that require heat and chemical resistance.

To understand how Pyrex is unique it is important to understand the nature of glass itself. Glass is a state of matter that has characteristics similar to both crystalline solids and liquids. On a macroscopic level glass appears to be like solids. It is rigid and remains in one piece when removed from a container. However, on a molecular level, glasses are more like liquids. In crystalline solids, molecules are arranged in an orderly fashion. In liquids they are randomly arranged. This random arrangement is also a characteristic of glass.

Glass is typically made by heating crystalline compounds to temperatures high enough to melt them. Melting breaks the ordered molecular structure, leaving them in a disordered state. When the melted material is cooled, the molecules become locked in place before they can reform in the ordered crystalline structure. The properties of a specific glass such as hardness, brittleness, clarity, and chemical and thermal resistance are dependent on its chemical composition.

When Pyrex was being developed, scientists were trying to create a glass composition that had a high thermal resistance. At some point it was discovered that glass compositions with boron could be heated to high temperatures without breaking. Boron, which is the fifth element on the periodic chart, has the unique ability to create a variety of chemical bonds. When bonded with oxygen it can create a three dimensional structure that is strong. In a glass composition, this extra strength gives it thermal and chemical resistance that makes it useful for cooking applications, thermometers, and laboratory equipment. Pyrex also has a low alkali content that gives it high corrosion resistance.

History

While the exact date people found that sand could be combined and melted with other materials to produce glass is not known, its discovery was likely accidental. Formal processes for glassmaking have been known for over 3,000 years. In Mesopotamia, archeologists have uncovered clay tablets that contain ancient "instructions" for making glass in furnaces. Throughout history, glass production technology became more sophisticated. People steadily discovered the best proportions to combine the raw materials and also learned manufacturing practices like glass blowing.

During the early twentieth century, kerosene lanterns were widely used for streetlights and railroad signaling devices. Unfortunately, the glass used for making these lanterns was sensitive to the heat of the flame and would often break. Scientists began searching for glass formulas that could withstand heat.

The first experiments led to the discovery that when boric acid was present in the raw materials, the glass was more heat resistant. These early formulas were chemically weak however, often breaking down in water. Work proceeded to find the right proportions of silica sand and boric oxide that would continue to be heat resistant and chemically stable. In 1912, an adequate formula was found. These glasses, called borosilicates, were then introduced into lantern production. One of the original types of borosilicate glass introduced by the Corning Glass Works Company was brand-named Nonex.

The potential for this product in the area of cooking was discovered in 1913 by Dr. Jesse T. Littleton who worked at Corning. He gave his wife a casserole dish made out of Nonex, the precursor to Pyrex. It worked as well as a ceramic cooking dish and a new era in cooking ware had begun. The Nonex glass formula was revised to remove lead, and the ovenware was given to the Philadelphia Cooking School for more testing. A series of successful tests there led to the introduction of Pyrex ovenware in 1915. This same year the Corning Glass Works Company patented the formula and gave it the trademarked name Pyrex. It has been suggested that the term Pyrex was either a derivative of the word "pie" (referring to its original use) or the Greek "pyra," which means hearth. In both cases, the "ex" suffix was used to give it brand-name similarity to Nonex.

When World War I broke out, scientists who relied on German glass products found that the new Pyrex material met their needs for beakers, test tubes, and other laboratory glassware. Borosilicate glass has steadily been made more chemical, heat, and shock resistant. It has also been applied to numerous products such eyeglasses, telescopes, and electronic components.

Raw Materials

Three classes of materials are used in making Pyrex including formers, fluxes, and stabilizers. Formers are the main ingredients in all glassmaking. These are crystalline materials that, when heated high enough, can be melted and cooled to create glass. Fluxes are compounds that help lower the temperature required to get the formers to melt. Stabilizers are materials that help keep glass from crumbling, breaking, or falling apart. They are needed because fluxes typically destabilize glass compositions.

The primary formers used for making Pyrex include silica sand and boric acid. Silica sand is also known as silicon dioxide. It is a crystalline material and was probably the major component of the first glass used by humans. In a typical Pyrex glass composition, silicon dioxide makes up about 60-80% by weight.

Pyrex has a droplet in matrix phase structure. The silicon dioxide creates the basic matrix. The borate material creates the droplets within that structure. The borate former can come from a material like sodium tetraborate. Prior to manufacture, this compound is chemically reduced with sulfuric acid to create boric acid. When boric acid is mixed with silicon dioxide and heated, it oxidizes into boric oxide. Boric oxide is responsible for the unique Pyrex molecular structure. Boric oxide makes up anywhere from 5% to 20% of Pyrex glass.

Secondary ingredients used in glass production include fluxes, stabilizers, and colorants. Fluxes are included in glass mixtures because they reduce the melting temperature of the borosilicate glass. Fluxes that can be used in manufacture include soda ash, potash, and lithium carbonate. They make up about 5% of a Pyrex glass composition.

Unfortunately, fluxes also cause the glass to be more chemically unstable. For this reason stabilizers such as barium carbonate and zinc oxide are included. In Pyrex manufacture, about 2% aluminum oxide is added to make the glass stiffer when it is molten. Finally, to produce glass with different colors, silver compounds can be added.

The Manufacturing
Process

The manufacturing process can be broken down into two phases. First, a large batch of molten glass composition is made. Next, the glass is fed into shaping machines to create different types of glassware. The process moves at tremendous speeds and is quite efficient.

Batching

• Large batches of Pyrex glass are produced in a specified compounding area of the production plant. Here, glassmakers follow formula instructions and add the required raw materials in the correct proportions into large tanks. Prior to use, the raw materials are pulverized and granulated to a uniform particle size. They are stored in batch towers. The materials are mixed together and heated to temperatures over 2,912°F (1,600°C). This high temperature melts the ingredients and allows them to thoroughly mix to create molten glass. However, the mixture typically requires longer heating—up to 24 hours—to remove excess bubbles that can lead to a weaker structure.

Forming

• The batch tanks are designed so that the molten glass will flow slowly toward the working end of the tank. This end of the tank is connected to continuous feed forming machines. As the glass moves from the tank it looks like a thick, red-orange syrup. The forming machines work the material quickly because as it cools it becomes rigid and unworkable. Typical glass processing machines blow, press, draw, and roll it into various shapes.
• The forming process used depends on the final product. Glass blowing is used to create thin-walled products like bottles. A bubble of the molten glass is put inside a two-piece mold. Air is forced into the mold, which presses the glass against its sides. The glass cools inside the mold and conforms to the shape. Glass pressing is used to create thicker pieces of glass. The molten glass is put into a mold and a plunger is lowered which forces the glass to spread and fill the mold. Drawing is used to create tubing or rods. In this process molten glass is drawn down over a hollow cone called a mandrel. Air is blown through it to keep the tube from collapsing until the glass becomes rigid. For glass sheets, like windows, a rolling process is used.
• After the product is formed, it is cooled and polished. It may then be decorated with various printing or markings and fitted with plastic pieces if necessary. The glass product is then checked for imperfections, put in protective boxes and shipped out to customers. Depending on the size of the batching tank, as much as 700,000 lb (317,520 kg) of glass product can be produced in one year.

Quality Control

Since the quality of the glass depends on the purity of the raw materials, manufacturers employ quality control chemists to test them. Physical characteristics are checked to make sure they adhere to previously determined specifications. For example, particle size is measured using appropriately meshed screens. Chemical composition is also determined with an IR or GC. Other simple checks that are done on the raw materials include color checks and odor evaluations. During production of a glass product, inspectors watch the glass products at specific points on the manufacturing line to ensure that each product looks correct. They notice things such as cracks, flaws or other imperfections. For certain products, the thickness of the glass is measured.

Byproducts/Waste

Since Pyrex is made from compounds that become oxides when heated, air pollution is a potential problem. A variety of byproducts may be released during manufacture including nitrates, sulfates, and chlorine. These chemicals can react with water to form acids. Acid rain has been shown to cause significant damage to manmade structures as well as natural ecosystems. One method glassmakers use to reduce pollution is by making glass compositions that have lower melting temperatures. Lower temperatures reduce the amount of volatilization thereby reducing the amount of gaseous pollutants. Another pollution control is the use of precipitators that are installed in chimneys. These devices help reduce air pollution by filtering out solids that persist in smoke and vapor created by the melting process. Waste-disposal drains are monitored to ensure that only allowable amounts of factory waste are released into the environment. This helps prevent water pollution.

An additional method of pollution control is the use of ventilators. These devices are also called regenerators because they help recover and recycle heat energy consumed during manufacture. This has the double effect of reducing air pollution and lowering production costs. Other cost reducing and environmentally sound techniques employed include the use of electric heat instead of gas heat, and the incorporation of broken recycled glass during the production of new glass.

The Future

In the future, borosilicate glass manufacturers will concentrate on increasing sales and improving the production process. To increase sales, glass manufacturers will be involved in finding and promoting new applications for their products. This could require new glass formulations that have a range of characteristics from clarity, melt point, and shatter resistance. From a production stand-point, future improvements will focus on increasing manufacturing speeds, minimizing chemical waste, and reducing overall costs.

Where to Learn More

Books

Bansal, N. P., and R. H. Doremus. Handbook of Glass Properties. New York: Academic Press, Inc., 1986.

Kirk-Othmer Encyclopedia of Chemical Technology. Vol. 12. New York: John Wiley & Sons, 1994.

Mazurin, 0. V. Handbook of Glass Data. New York: Elsevier Science Publishing Co., 1991.

Rogove, S. T., and M. B. Steinhauer. Pyrex by Corning: A Collector's Guide. New York: Antique Publications, 1993.

Other

Corning Museum of Glass Web Page. 1 October 2001. <http://www.cmog.org>.

United States Patent 4,075,024. Colored Glasses and Method. 1976.

[Article by: Perry Romanowski]

Trade name for heat- and shock-resistant borosilicate glass, developed by Eugene Sullivan and William Taylor working for Corning Glass, 1915.

For the programming language, see Pyrex (programming language).

Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915. According to Carroll Gantz^[1], Dr. Jesse Littleton of Corning discovered its cooking potential by presenting his wife with a makeshift casserole made from a cut down Nonex (a low expansion glass developed in 1908 by Dr. Eugene Sullivan) battery jar. Corning then removed the lead that was present at the time, and Pyrex was born.

Originally, Pyrex was made from thermal shock resistant borosilicate glass. In 1998, Corning sold its consumer products division which subsequently adopted the name World Kitchen. Pyrex kitchen glassware manufactured and licensed for sale in the United States is now made of tempered soda lime glass at the World Kitchen facility in Charleroi, Pennsylvania.^[2] Pyrex products for the European Union continue to be made of borosilicate glass in France.^[3] Pyrex laboratory glassware is also still made of borosilicate glass.^[4]

Contents 1 History of the Pyrex Brand 2 Design 3 Composition 4 Use in laboratory ware 5 Usage in telescopes 6 Controversies 7 Footnotes 8 References 9 External links

History of the Pyrex Brand

Though borosilicates had been produced before the Pyrex brand, the name Pyrex is widely used as a genericized trademark for the material. Corning sold off its Consumer Products division in 1998 as World Kitchen but retained the Pyrex brand name, licensing it to World Kitchen and other companies that produce Pyrex-branded cookware (e.g. Newell Rubbermaid's Newell Cookware Europe).^[5] The brand in Europe, the Middle East and Africa is currently owned by ARC International who acquired the European business in early 2006 from Newell Rubbermaid who in turn had acquired it from Corning in the 1990s.^[6]

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

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.^[7]

Pyrex kitchen products in Europe made and sold by a subsidiary of ARC International tableware company are made from borosilicate glass.^[8]

Design

In 1948 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.

Composition

Except for the Charleroi, PA-made Pyrex glass cookware, older Pyrex and European Pyrex is still made of borosilicate glass. According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 4% boron, 54% 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.

Use in laboratory ware

Because Pyrex borosilicate glass has a high thermal resistance it is often used in the manufacture of laboratory ware. In Europe, SciLabware Limited manufacture more than 800 items under the Pyrex brand name including beakers, bottles, flasks, dishes and test tubes.

Usage in telescopes

Because of its low expansion characteristics, Pyrex 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.^[12]

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.

The University of Arizona is currently engaged in the fabrication of seven 8.4 meter optical blanks for its Giant Magellan Telescope using borosilicate glass.^[13]

Controversies

In May 2008, in a report broadcast on a Chicago TV channel, Pam Zekman reported that people have complained that Pyrex bakeware has shattered or even exploded during ordinary use. US Senator Dick Durbin and US Congresswoman Jan Schakowsky from Illinois have called on the Consumer Product Safety Commission to find out if there is a problem with Pyrex.^[14] Zekman's segment did not include any reports on actual laboratory tests of Pyrex glassware. The segment went on to say that none of the US hospital emergency rooms surveyed by the Consumer Product Safety Commission reported treating any injuries in 2005 or 2006 that were due to breakage of Pyrex glassware. The CPSC has nonetheless received a number of reports of failures directly from consumers. The company has a web page devoted to these and other consumer issues.^[15][16]

Footnotes

1. ^ Pyrex History
2. ^ [1]
3. ^ "Manufacturing History". Pyrexware.com. http://www.pyrexware.com/thetruthaboutpyrex/manu.htm. Retrieved Feb. 11, 2009. 
4. ^ [2]
5. ^ "ARC International page". Hoover's. http://www.hoovers.com/arc-international/--ID__103296--/free-co-factsheet.xhtml. Retrieved 2007-08-01. 
6. ^ Hibberd, Susan (2007). The Little Book of Collectable British Pyrex. Exposure Publishing. ISBN 184685556X. 
7. ^ Mathews, MM (1957). "title unknown". American Speech 32 (4): 290. 
8. ^ "Glass Ovenware". ARC International. 2005. http://www.arc-international-cookware.com/en_Glass_Ovenware.html. Retrieved 2008-03-17. 
9. ^ "Composition of Pyrex Glass". National Institute of Standards and Technology. n.d.. http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=169. Retrieved 2008-03-17. 
10. ^ "How Pyrex is Made". MadeHow.com. n.d.. http://www.madehow.com/Volume-7/Pyrex.html. Retrieved n.d.. 
11. ^ "Borosilicate glass". http://www.pulleshanique.com/02_borosilicate-glass.htm. Retrieved 2009-01-08. 
12. ^ "Caltech Astronomy: History - 1908–1949". Caltech. nd. http://www.astro.caltech.edu/observatories/palomar/history/. Retrieved 2008-03-17. 
13. ^ [3]
14. ^ [4]
15. ^ [5]
16. ^ Exploding Pyrex at Snopes.com.

References

• Rogove, ST; Steinhauer, MB (1993). Pyrex by Corning: A Collector's Guide. Antique Publications. ISBN 0-915410-94-X. 
• Gantz, Carroll, (2005). DESIGN CHRONICLES: Significant Mass-produced Products of the 20th Century, Schiffer Publishing, ISBN 978-0764322235

External links

• Pyrex official website
• Vintage Pyrex Reference Guide

v • d • e Glass makers and brands Contemporary companies Anchor Hocking · Arc International · Ardagh · Armashield · Asahi · Aurora Glass Foundry · Baccarat · Blenko Glass Company · Bodum · Corning · Dartington Crystal · Daum · Edinburgh Crystal · Fanavid · Fenton Art Glass Company · Firozabad glass industry · Franz Mayer · Glava · Glaverbel · Hardman & Co. · Heaton, Butler and Bayne · Holmegaard Glassworks · Holophane · Hoya · Kingdom of Crystal · Kokomo Opalescent Glass Works · Kosta Glasbruk · Libbey Owens Ford · Liuli Gongfang · Iittala · Luoyang · Johns Manville · Mats Jonasson Målerås · Moser Glass · Mosser Glass · Nippon Sheet Glass · Ohara · Orrefors Glasbruk · Osram · Owens Corning · Owens-Illinois · Pauly & C. - Compagnia Venezia Murano · Phu Phong · PPG · Pilkington · Preciosa · Quinn Group · Riedel · Royal Leerdam Crystal · Saint-Gobain · Samsung Corning Precision Glass · Schonbek · Schott · Shrigley and Hunt · Steuben Glass · Sterlite Optical Technologies · Swarovski · Tyrone Crystal · Val Saint Lambert · Verrerie of Brehat · Waterford · Watts & Co · World Kitchen · Xinyi Glass · Zwiesel Historic companies Bakewell Glass · Belmont Glass Company · Boston and Sandwich Glass Company · Carr Lowrey Glass Company · Cambridge Glass · Chance Brothers · Clayton and Bell · Dunbar Glass · Fostoria Glass Company · General Glass Industries · Alexander Gibbs · Grönvik glasbruk · Hazel-Atlas · Heisey · Hemingray Glass Company · Knox Glass Bottle Company · Lavers, Barraud and Westlake · Manufacture royale de glaces de miroirs · Morris & Co. · Old Dominion Glass Company · James Powell and Sons · Ravenhead glass · The Root Glass Company · Sneath Glass Company · Ward and Hughes · Westmoreland Glass Company · Whitall Tatum Company · White Glass Company · Worshipful Company Glassmakers John Adams · Richard M. Atwater · Frederick Carder · Irving Wightman Colburn · Henry Crimmel · Henry Clay Fry · Friedrich · A. H. Heisey · Libbey · Antonio Neri · Alastair Pilkington · Salviati · Otto Schott · S. Donald Stookey · W. E. S. Turner · John M. Whitall Trademarks and brands Bohemian glass · Bomex · Burmese glass · Chevron bead · Corelle · CorningWare · Cranberry glass · Cristallo · Duran · Endural · Favrile · Fire King · Gold Ruby · MACOR · Murano glass · Opaline glass · Pyrex · Ravenhead glass · Tiffany glass · Vitrite · Vitrolite · Vycor · Waterford Crystal · Wood's glass · Zerodur

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - glas, der kan modstå stærk varme

Nederlands (Dutch)
pyrex

Français (French)
n. - Pyrex

Deutsch (German)
n. - feuerfestes Glas

Ελληνική (Greek)
n. - πυρέξ

Italiano (Italian)
pyrex

Português (Portuguese)
n. - pirex (m)

Русский (Russian)
лабораторное стекло

Español (Spanish)
n. - pirex, cristal resistente al calor

Svenska (Swedish)
n. - ugnsfast glas

中文（简体）(Chinese (Simplified))
派莱克斯玻璃

中文（繁體）(Chinese (Traditional))
n. - 派萊克斯玻璃

한국어 (Korean)
n. - 파이렉스

日本語 (Japanese)
n. - 耐熱ガラス, パイレックス

العربيه (Arabic)
‏(الاسم) زجاج يتحمل النار و الحرارة‏

עברית (Hebrew)
n. - ‮זכוכית חסינת-אש, פיירקס‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.