Can Your Glass Bakeware Explode?

We recently heard a story from one of our friends that her casserole glass dish exploded as she took it out of the oven. She wasn’t hurt but the glass and food was everywhere. That sounds crazy dangerous, so we decided to look a bit deeper into this issue.

Glass bakeware has been around ever since the early 1900s, and there have been few problems with it. But, no matter how safe you try to be, sometimes Murphy will have his little joke. For seemingly no reason at all, a glass bakeware item will spontaneously explode, redecorating your kitchen with little bits of food. It is rare, but it does happen.

When Pyrex came out with the first glass pie pans in the early 1900s, one of the ingredients in them was borosilicate. It is what made them heat-resistant. But…. nothing is foolproof. Occasionally, a Pyrex or many other popular glass bakeware brands would shatter, sending sharp shards of glass everywhere. But it was never enough of a problem to give much attention to. In the 1980s, glass bakeware manufacturers switched to using soda lime, instead of borosilicate. If the unit did shatter, the soda lime causes it to break into bigger and duller pieces.

So, why do glass bakeware item sometimes shatter? Dropping them is one of the major causes, obviously, but the other causes can be chalked up to the sometimes unpredictable nature of crystalline structures. Crystals are notoriously temperature and vibration sensitive, and the hotter they get, the more pronounced the properties get. It is very easy, especially if you are pressed for time, to unthinkingly take a glass casserole dish out of the refrigerator and just pop it into a hot oven. This can cause a spontaneous GFE (Glass Fragmentation Event), as well as induce some language not normally used in polite company. So here are some tips to help you avoid the risk of spontaneous glass-knapping:

  • Avoid sudden temperature changes, such as direct from freezer or refrigerator-to-oven, or oven-to-sink.
  • Never, I repeat, never add liquid to hot glass bake-ware.
  • Never use glass bake-ware at temperatures hotter than 350°F.
  • Never use glass bake-ware under a broiler, on a stove-top burner, or a toaster oven.
  • Never set a hot glass bake-ware nit on a cool surface. Always set them on a towel or cooling rack.
  • Allow your oven to pre-heat before placing a glass bake-ware unit in it.
  • Do not bump, wipe, or attempt to scrape a hot glassware baking unit until it has completely cooled.
  • Never run water in a hot glass bake-ware unit, or set it in the sink until it has completely cooled.

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