Why is pyrex glass different to normal glass

According to Davis, the CPSC is unable to release information about specific companies without following a public disclosure process. However, the SaferProducts. In many cases, the instances of exploding Pyrex reported to SaferProducts.

Since customer reviews can last forever online, the mounting complaints about exploding tempered glass can seem unsettling, even though the occurrence is quite rare according to the CPSC and multiple glass experts we spoke to. But when you consider the thousands of pieces made each day in a glass factory, the number of incidents reported is remarkably small. In most cases, we think the benefits of tempered glass—its durability and safer breakage patterns—outweigh the danger.

Other than being completely surprised and a little annoyed about having to clean tiny bits of glass out of my sink , I was unhurt, not even a scratch.

For example, a calculation published by the American Ceramic Society found that borosilicate glass can withstand a sudden temperature change of up to about degrees Fahrenheit, whereas tempered glass can withstand a temperature change of about degrees. The publication references the tests performed by Consumer Reports , which used dry sand heated in casserole dishes. However, since sand gets much hotter than food, some experts say these tests which are often cited in news stories about Pyrex are too extreme and are not an accurate representation of durability under normal use.

According to excerpts provided to us by Hugh Rushing, former executive vice president of the CMA, the CMA tests suggest that glass bakeware should be able to withstand being abraded with sandpaper to simulate wear over time , heated in the oven for 20 minutes, and then submerged in a water bath with a temperature difference of degrees Fahrenheit. This procedure was developed in conjunction with a committee of glass manufacturers and industry consultants, and it has been tested on a variety of glass samples from all the major glass producers, with the results submitted to an independent lab for analysis.

And though adhering to these standards is voluntary, Rushing told us that a majority of cookware retailers and manufacturers subscribe to them. It sounds obvious, but you can help extend the life of your glass bakeware and tableware by treating it with care.

You may be subjecting your tempered wares to extreme temperature changes and other abuses without even realizing it. Pyrex tempered glass is made when the cleaned and polished product is reheated to near its annealing temperature and then rapidly cooled on the outside by jets of air while the inside is allowed to cool more slowly. This creates a surface tension that significantly changes the characteristics of the glass.

Tempering is done on finished products because once it is tempered, glass cannot be cut or shaped without causing the piece to shatter. Glass strength refers to impact resistance. Fully tempered glass is four to six times stronger than regular annealed glass.

Regular annealed glass can break into long, hazardous shards with sharp edges. Pyrex is made by the low coefficient expansion of borosilicate glass whereas glass is blown and pressed to prepare it for the molding process. When ordinary glass acquires some new characteristics due to some tempering and other processes, it is called Pyrex. The tempering process when applied to the finished glass products called Pyrex makes it four to six times stronger than the regular glass product. The heat resistant quality to bear up to degrees F makes the Pyrex products ideal for the use in the kitchen especially for cooking or baking purposes.

Pyrex glass breaks into a smooth pattern known as dicing and shatters down into small cubical pieces whereas glass can break into hazardous sharp edged long pieces. Pyrex was produced in by Corning In. They produce heat resistant products like baking trays, measuring cups and tea pots etc. Since the ordinary glass does not have much heat resistant qualities, we do not use them directly in contact with too much heated or cold temperatures.

Simple glass products are not suitable for kitchen use because any sudden change in the temperature can cause the glass to break immediately such as pouring of boiling milk directly from the stove to a cold glass or putting the cold glass dish into the hot oven directly etc. However, like all glassware, some security measures should be followed to avoid any mishap or sudden accident. Pyrex should also be used along with some safety measures to save the individual from risking himself to an injury or product damaging.

Frozen Pyrex dishes should be thawed before they are used for baking and hot vessels should be allowed to cool down before refrigerating. Pyrex products at room temperature can withstand direct heat well but regular glass products are not suitable to to be put directly on the stove or any other heat sources. This is where the controversy really heats up. The vast majority of glass products are made of soda-lime glass: window panes, jars, bottles, all kinds of glass.

Soda-lime glass is cheaper to make than borosilicate glass, which is undoubtedly why Pyrex started experimenting with it. Thermal shock is what happens when a temperature change causes different parts of a material to expand at different rates, and the resultant stress can cause the material to crack.

If the temperature change happens rapidly materials like glass can shatter or seem to explode. Resistance to thermal shock is part of why Pyrex became so popular for cookware; you could move a hot glass pan into a cool spot without worrying about it cracking or shattering.

Pyrex cookware currently sold in the United States goes through a thermal tempering process. In theory, this should strengthen the glass. In practice, the difference between the performance of borosilicate glass and soda-lime glass is significant.

When asked about the science behind the glass, Dr. John C. Mauro, a professor of engineering and materials science at Penn State, said in an email that the coefficient of thermal expansion CTE is the main parameter used to measure thermal shock resistance. A higher CTE number means the material is less resilient to thermal shock. But soda-lime glass has a CTE of 9 to 9. Mauro knows his glass, too.

Before taking his faculty position at Penn State, he spent nearly two decades working at Corning, where he was one of the inventors of Gorilla Glass. Mauro has also co-authored academic papers on the glass chemistry of Pyrex, and he is the editor of the Journal of the American Ceramics Society.

Based on his extensive knowledge of the material, Mauro actually makes the science behind soda-lime glass and heat sound even more damning. He went on to note how soda-lime glass is tempered to improve its strength.