All you need is an extra container and a working faucet to check if your glass jar is microwavable -- and to prevent safety hazards in the kitchen.
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Can You Put Glass In The Microwave?

Microwave-safe glass is specifically designed to withstand the heat and energy of microwaves without cracking, shattering, or ...
Most glass bowls are microwave-safe, but not all, and using the wrong type could lead to cracks or shattered glass in your microwave. Tempered glass, like Pyrex, is specially designed to withstand ...