How does pyrex glass work

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.

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. Unfortunately, fluxes also cause the glass to be more chemically unstable.

For this reason stabilizers such as barium carbonate and zinc oxide are included. Finally, to produce glass with different colors, silver compounds can be added. 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. 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 A diagram of the production of Pyrex. 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. 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.

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. Bansal, N. Handbook of Glass Properties. New York: Academic Press, Inc.

Kirk-Othmer Encyclopedia of Chemical Technology. Mazurin, 0. Handbook of Glass Data. Rogove, S. Pyrex by Corning: A Collector's Guide.

Will it break if heated or cooled? What does it look like when it breaks? Untreated soda-lime glass is far more likely than the others to break from a tumble off your table. This shock causes different parts of the glass to expand at different rates and often crack from stress, making soda-lime glass a poor candidate for bakeware. Tempered glass is soda-lime glass that has been heat-treated for durability.

During that heat-tempering process , the exterior of the glass is force-cooled so that it solidifies quickly, leaving the center to cool more slowly. As the inside cools, it pulls at the stiff, compressed outer layer, which puts the center of the glass in tension. And borosilicate glass is more expensive to manufacture than tempered or soda-lime glass.

So if something, such as a crack or flaw, disrupts the compressed outer layer and reaches the tensile zone, that throws off the balance, and the entire piece crumbles into tiny cube-shaped pieces unlike untreated soda-lime glass, which breaks into shards. Surface damage can result from any rough treatment of glass, such as repeatedly scratching it, dropping it, or banging it against another item in the dishwasher. This damage can weaken the glass without fully breaking it.

If you want to get really nerdy, scientists in fracture mechanics call this kind of damage subcritical crack growth. It sounds counterintuitive, but LaCourse also said that although tempered glass is more durable than untreated soda-lime, it actually scratches more easily because the tempering process makes it less dense.

Handling tempered wares or any glassware with care is of the utmost importance. Thermal stress is another factor that can cause glass to break spontaneously. If one part is expanding or contracting more or less than the other, at the region in between [is] where the stress happens. Manufacturing flaws are imperfections in the glass that develop when the piece is made.

These include:. Some publications such as ConsumerAffairs have cited this weakening as one possible reason for spontaneous fracture. To me, what we have to worry about are the flaws in the glass surface. Corning Glass Works wasn't the first company to develop temperature-resistant glass, however. In the s, a German scientist, Otto Schott, developed a low-expansion glass called borosilicate glass, but used it mostly to make products for industrial and scientific settings, such as laboratory glass.

Corning developed its own recipe in , mostly selling it to railroad companies for signal lanterns. Corning held a patent for its formula for borosilicate glass from until ; when the patent expired, the company came up with a new formula for heat-resistant glass, alumino-silicate glass.

Company accounts suggest that the name Pyrex came from the company's tradition of using "ex" in its glass formulas Corning's first heat-resistant glass was called Nonex , according to Regan Brumagen, public services librarian and co-curator of the exhibition at the Corning Museum of Glass.

She adds that the company was probably also playing with the prefix "pyro," as early ads had the words "fire-glass" printed beneath Pyrex. Early products included the typical Pyrex casserole dishes, as well as pie plates, shirred egg dishes, custard cups, loaf pans, oval baking dishes, cut-glass teapots and engraved dishes.

In , the Pyrex liquid measuring cup was introduced, though it didn't look like the one commonly used today it had two spouts on opposite sides, with a handle in between. Victoria Matranga, author of America at Home: A Celebration of 20th Century Housewares and design programs coordinator at the International Housewares Association, notes how well the early designs have held up: "The measuring cup and the oblong and square bakers are truly iconic.

But Pyrex wasn't an overnight sensation. The products were expensive; the production process was initially just semi-automated—meaning the machines were still manned by factory workers. An early advertisement shows a maid, not a housewife, using Pyrex, indicating who Corning felt was the ideal market for the cookware.

Pyrex could withstand the heat of the oven as well as the cold of the refrigerator, but in the '20s, only well-off families had homes wired for electricity and refrigerators were considered a luxury. After World War I, home economics was emerging as a profession, and many women were earning college degrees in this progressive, multidisciplinary field, which applied the principles of science to homes, communities and families.

This training prepared women for jobs in academia, public education, industry and government. Corning, like other companies, used the trend to its advantage, hiring domestic professionals to test and promote its products. In , Corning hired a full-time scientist and home economist, Lucy Maltby. In the years that followed, Maltby established a test kitchen to evaluate new products and became an advocate for the consumers who used Pyrex, fielding thousands of letters.

Maltby and her test kitchen team "had a profound impact on the functional design of Pyrex products," Brumagen says. Maltby first convinced the company to redesign its cake pans, adding handles and volume, and making the diameter smaller so that two cake pans could fit side-by-side in a standard oven. Maltby's influence was so strong that Corning executives had a mantra: "What does Lucy think? In the '30s, Pyrex became affordable for the masses, when the production process became fully automated.