Borosilicate glass is a type of glass with silica and boron trioxide as the main glass forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (~3 × 10−6 K−1 at 20 °C), making them resistant to thermal shock, more so than any other common glass. (from Wikipedia)

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Borosilicate glass is less subject to thermal stress and is commonly used for the construction of reagent bottles. Borosilicate glass is sold under such trade names as Simax, Borcam, Borosil, Suprax, Kimax, Heatex, Pyrex, Endural, Schott, or Refmex, Kimble.

History

Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century. Otto Schott is also the founder of today’s SCHOTT AG, which sells borosilicate glass under the brand name DURAN® since 1893. Another manufacturer of DURAN® is the DURAN® Group. After Corning Glass Works introduced Pyrex in 1915, the name became a synonym for borosilicate glass in the English-speaking world. However, borosilicate glass is the name of a glass family with various members tailoring completely different purposes. Most common today is borosilicate 3.3 glass like SCHOTT Duran and Pyrex by Corning.

In addition to quartz, sodium carbonate and aluminum oxide traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass. The composition of low-expansion borosilicate glass, such as those laboratory glasses mentioned above, is approximately 80% silica, 13% boric oxide, 4% sodium oxide and 2–3% aluminum oxide. Though more difficult to make than traditional glass due to the high melting temperature required (Corning conducted a major revamp of their operations to manufacture it), it is economical to produce. Its superior durability, chemical and heat resistance finds excellent use in chemical laboratory equipment, cookware, lighting and, in certain cases, windows.

Pyrex_newspaper_ad_1922Pyrex (trademarked as PYREX) is a brand introduced by Corning Inc. in 1908 for a line of clear, low-thermal-expansion plastic borosilicate glass used forlaboratory glassware and kitchenware. Pyrex sold in the United States is made of tempered soda-lime glass; outside of North America the costlier borosilicate is still used.

Corning no longer manufactures or markets PYREX-branded borosilicate glass kitchenware and bakeware in the US. World Kitchen, LLC, which was spun off from Corning in 1998, licensed the pyrex (all lower case) brand for their own line of kitchenware products—differentiated by their use of clear tempered soda-lime glass instead of borosilicate.

The European manufacturer of Pyrex, Arc International, uses borosilicate glass in its Pyrex glass kitchen products;[1] however, the U.S. manufacturer of Pyrex kitchenware uses tempered soda-lime glass.[2] Thus Pyrex can refer to either soda-lime glass or borosilicate glass when discussing kitchen glassware, while Pyrex, Bomex, Duran, TGI and Simax all refer to borosilicate glass when discussing laboratory glassware. The real difference is the trademark and the company that owns the Pyrex name. The original Corning ware made of borosilicate glass was trademarked in capital letters (PYREX). When the kitchenware division was sold, the trademark was changed to lowercase (pyrex) and switched to low thermal-expansion soda-lime glass. The bottom of new kitchenware and old kitchenware can be inspected for an immediate difference. The scientific division of Pyrex has always been using borosilicate glass. (from Wikipedia)


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