Why Glass Oven Bakeware Can Shatter
Oven-rated heat-resistant glass bakeware was first introduced to the market in the 1900's in the U.S. with the invention of Pyrex pie plates. It was so popular that the market quickly expanded to other styles of affordable heat-resistant bakeware and it became the homemaker's favorite dish for oven baking or refrigerated desserts.
There are basically two major glass bakeware manufacturers in the U.S. - Anchor Hocking and World Kitchen. One of the original ingredients used in the manufacture of glass bakeware is borosilicate.
According to the Anchor Hocking site, the change to soda lime (from borosilicate) was made about thirty years ago in an effort to make their bakeware safer. World Kitchen also followed suit, but surprisingly, some European manufacturers continued to use borosilicate in their bakeware.
Safety being the reason for the change in recipe, manufacturers wanted their bakeware to break in a less hazardous way, should it break at all. And yes, the risk has always been there - after all - it's glass, tempered or not. Glassware made with borosilicate tends to shatter and scatter sharp shards of glass, where soda lime glass breaks in larger, duller pieces. According to Anchor Hocking, soda lime glass is also more resistant to breakage when it comes into contact with hard surfaces or sharp utensils. So the switch in materials was justified for safety reasons and both manufacturers stand by claims that their bakeware is safe to use.
Consumer Reports Testing
Consumer Reports conducted a 12-month investigation that included testing of U.S. and European bakeware, as well as gathering information from manufacturers, experts and consumers. You can read the full report, but in short, bakeware manufactured in the U.S. was more prone to shattering than those made in other countries, under certain conditions. Their findings left room for concern and they urged the Consumer Protection Safety Commission (CPSC) to look into the safety of glass bakeware, especially given the change from borosilicate to soda lime in their construction. To get the full testing details, read the Consumer Reports Article.
Is Glass Bakeware Safe To Use?
According to the U.S. manufacturers, they feel their products are safe to use, but you have to decide if it's worth the risk. It's totally understandable that tempered glass products can and do break occasionally, especially if the glass should weaken for any reason.
The risk was present when the first glass Pyrex pie plate was made using borosilicate; it just was not an issue. But with the right care, you can minimize the risk and understand that certain conditions can make it more susceptible to shattering.
Note that with the best of care, a heat-resistant glass bowl or bakeware could still break or shatter - there's absolutely no guarantee that it won't. If you feel uneasy using your glass bakeware in the oven, keep it for non-baked desserts and use metal bakeware for everything else.
How to Minimize the Risks of Glass Bakeware Shattering
New bakeware comes with instructions for use and care and they do vary with brands. Unfortunately, we often discard this label and it's soon forgotten. Here are some general tips for safe use of glass bakeware and follow links for specific instructions for Anchor Hocking or World Kitchen Pyrex brand products.
- Avoid changes in temperature; no going from freezer to oven, or from oven to sink
- Do not add liquid to hot glassware
- No higher heat than 350 degrees (this has always been my standard)
- Do not place hot bakeware on cold or wet surfaces, or countertop, stovetop; place instead on a towel or cutting board, cooling rack
- Do not use on stovetop, under broiler or in a toaster oven
- Allow pans to cool completely before immersing in water
- Use care not to bump it, poke or scratch it with utensils
- Allow oven to preheat before adding the bakeware
- Read Anchor Hocking Care Information
- Read World Kitchen Pyrex Bakeware Care Tips