Pyrex is glassware. Like all glass products, you should be careful when handling it. You don’t haphazardly drop it, or else it will shatter. You also don’t cook food with it, use a pot. High temperatures can break it as well as a high-enough fall.
With that said, can you reheat food with Pyrex using a microwave? Indeed, can you microwave pyrex? Keep on reading to find out. The short of it is you shouldn’t microwave Pyrex cold and you’re good to go.
Can You Microwave Pyrex?
Pyrex bakeware, like with all glass products, is susceptible to breakage at high temperatures. With that said, reheating temperatures on food that don’t reach superheated degrees of hotness should be fine. If the microwave temperatures are too high, it will break as if you threw it at a wall.
The Rules of Pyrex Safety and Handling
As many microwave users are aware, ceramic and glass are among the recommended microwaveable materials. However, you should watch out for the primary risks of cooking or heating using glassware. They include:
- Burning or scalding on your part when handling hot Pyrex glassware.
- You dropped the Pyrex on the floor or you dropped a hard object unto it, causing it to shatter.
- The glass shattering because you heated it up while it’s cold, which is a sudden temperature change.
Therefore, you should particularly be careful when heating up cool Pyrex glassware taken straight from the refrigerator with a microwave due to how glass shatters when its temperature changes from hot to cold or cold to hot suddenly.
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What is Pyrex Anyway?
Pyrex® is an American-made glassware brand known for its safety, practicality, durability, consistency, stain-proof nature, durability, and affordability. It’s one of the ten products “surprisingly” still made in America instead of overseas like China according to 247wallst.com.
Compared to other brands of glassware, America’s Pyrex has thicker and harder glass made of soda-lime glass (formerly borosilicate glass) that’s marked by the Consumer Product Safety Commission as safe.
Glassware by Pyrex can be used for cooking, warming, baking, and reheating food inside microwave ovens as well as convection or conventional ovens that require preheating. They’re made for it. There are caveats regarding their usage for cooking though.
The Caveats of Using Pyrex
Among them is never to microwave a cold piece of Pyrex glassware straight from the refrigerator because it could undergo thermal shock and break. Pyrex glass is dishwasher-safe as well as microwaveable. Make sure to use non-abrasive cleansers and nylon or plastic cleaning pads when cleaning it by hand.
This product should only be used at home. Don’t use it for commercial, industrial, or camping use. Rugged treatment will break it. The plastic lids that come with it are BPA-free and should only be used for storage and microwaving only.
What is Thermal Shock?
Thermal shock happens when you microwave cold Pyrex straight from the fridge. Why? It’s because all glass—whether it is borosilicate glass or soda lime glass—will have various parts of the glassware material expand by different amounts when its temperature changes in a rapid fashion.
Moreover, this uneven expansion and stress due to sudden temperature changes “shocks” the system of the container or vessel, leading to thermal shock and resulting in the glassware breaking or outright shattering. No glassware can resist sudden changes in hotness or coldness.
Is It Safe to Use Pyrex in the Microwave in Light of Thermal Shock Risk?
As long as you microwave Pyrex at room temperature you’re good to go. As long as you don’t place a freshly microwaved Pyrex container into the freezer, it should also be safe. Its soda-lime glass is perfectly microwave-safe.
The only reason ceramic is better than glass at dealing with thermal shock is that the material doesn’t heat up easily. Glass does, so for safety’s sake don’t place it on your stove or with a burner below it to cook your food.
Ensure Mindful Changes in Glassware Temperature
Avoid rapid changes in temperature because when the glass experiences a thermodynamic reaction, it will become stress out enough to abruptly expand in certain areas then break due to all the inconsistency.
Aside from the obvious avoidance of microwaving cool glassware, you should be mindful when changing the temperature of your Pyrex. If you can’t wait for the Pyrex to cool down, microwave it using a low power level at first then gradually raise the level.
Work your way up to high power. Don’t add hot liquid to cool glassware or cool liquid to hot glassware either. Let the glass bowl or plate gradually cool down when hot or gradually reach room temperature when cold.
Is It True That Pyrex Made in the 20th Century is Likelier to Break When Microwaved?
No. Across the board, glassware today or in yesteryears all suffer from breakage due to sudden temperature changes. If there’s a sudden up-tick in broken glassware when microwaved, it’s less because of lower-grade glass and more because of higher-wattage microwaves.
Regardless, Pyrex and many other glass bakeware brands risk breakage due to what’s known as thermal shock. A cold piece of Pyrex glassware can break when hot. It is true though that originally, Pyrex was once made of borosilicate glass, which was replaced with tempered soda-lime glass.
Does the Change in Glass Material Mean Anything?
So does that mean that soda-lime glass is more breakable than borosilicate glass when microwaved? According to the Consumer Product Safety Commission, that’s bogus. They never claimed Pyrex glass as unsafe and instead mark it as safe.
All Pyrex glassware is made in the U.S.A. as well (to address rumors that it’s now being made on the cheap in China). The Pyrex brand’s owner, World Kitchen, is also based on the U.S. for good measure. It’s purely American-made and premium-quality all throughout.
The Nitty-Gritty
Pyrex can break when microwaved, but not because it’s now made of low-grade glass. Rather, all glassware that’s cold then suddenly heated up in your microwave oven should break or shatter. Don’t microwave cold glass because the sudden temperature change can break it.
This applies to all types of glassware, including Pyrex. It’s even a risk for other microwaveable materials such as ceramic, porcelain, and chinaware. Have a presence of mind when microwaving things. Or err on the side of caution and transfer your cold food on a room-temperature container.
References:
- David Mikkelson, “Does Pyrex Brand Bakeware Shatter?“, Snopes.com, September 18, 2009
- “Is Pyrex Microwave safe? (Research and Answers)“, ThePowerWoman.com, February 9, 2013
- “Pyrex Glass Use & Care“, Pyrexware.com, Retrieved April 24, 2021
- “Can You Microwave Cold Pyrex?” MicrowaveMealPrep.com, September 4, 2020
