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Are Mason Jars Microwave Safe? (Microwave Safety Tips)

3 Rustic Mason Jars with Moonshine

Many people use mason jars to store soups, sauces, and canned foods. However, when it comes time to reheat these items, many people wonder if it’s safe to heat the jars in the microwave. The short answer is yes. Most mason jars, especially modern ones, can withstand high temperatures without cracking or shattering. However, keep reading to learn how to tell if your jar is ready for the microwave and other tips that will help you have a better experience in the kitchen.

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What Mason Jars Are Microwave Safe?

Microwave-Safe Mason Jars

Many manufacturers considered the probability that people would put mason jars into the microwave and took steps to ensure that the jars wouldn’t crack or smash. In fact, many brands will stamp the glass with the words, “microwave safe,” so there is no question that you can use them in there. Besides the words or along with them, you might also see a symbol of wavy lines, which means you can use the jar in the microwave.

Antique Jars

If the jar does not have the words, “microwave safe,” on it, it might be an antique. Many people worry that antique jars made before the microwave was invented won’t hold up well because they might be made of a different type of glass that can’t handle the high temperatures that a microwave can create. While there can be a bit of truth to this concern, people have long used mason jars for canning, which requires incredibly high temperatures, so the glass will likely hold up just fine. However, if the glass appears especially old, use extreme caution when heating it in the microwave.

Mason Jars
Image By: Elly, Pixabay

How to Microwave a Mason Jar Safely

If you are using an older mason jar without the words, “microwave safe,” on it, we recommend heating it for 30-second intervals to help prevent the temperature from rising too quickly. This method also enables you to check the jar for signs that the glass is not holding up. If it is a microwave-safe jar, you can extend the heating to about 1 minute at a time, checking it in between intervals to stir the contents and ensure that no damage is occurring.

Sterilizing a Mason Jar

If you are using a new mason jar, wash it out to remove any contaminants, and look it over to ensure that there are no cracks or chips. Fill the mason jar with water, and heat it for 3–4 minutes to kill bacteria. Allow the jar to cool before rinsing it out. To clean the lid, boil it for several minutes.

Other Tips for Safely Microwaving a Mason Jar

  • Never microwave a mason jar with the lid on it, as metal is not safe to put in a microwave. Even a microwave-safe lid can cause pressure to build up, leading to an explosion.
  • Always use oven mitts or pads when removing a mason jar from the microwave so you don’t burn your skin.
  • Never place a mason jar into the microwave right after you take it out of the freezer. Instead, let it warm up for several minutes to reduce the risk of cracking.
  • Don’t reheat mason jars that are more than 60%–70% full. Cold food will expand and can bubble and splash, making a mess in the microwave.
  • Microwaving on high power seems to work best when heating food inside a mason jar.
  • Never microwave a cracked or chipped mason jar because it might shatter.
  • Microwaving for short bursts and stirring after each time is the best way to heat your food evenly and reduce pressure build-up.
  • If the sides of your mason jar are not clear, it might not be microwave safe.
  • As a test, heat an empty mason jar in the microwave for 1 minute. If it gets very hot, it isn’t microwave safe.
  • If you are worried, don’t microwave a mason jar unless it has a microwave-safe stamp on the glass.

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Most manufacturers make mason jars that are microwave-safe, so you can heat your food in them without worrying about cracks or breaks. Check the bottom or sides for the words, “microwave safe” or a symbol with wavy lines. If the glass is not clear, there is a good chance that it’s an antique jar and may not be able to stand up to the high temperatures that a microwave can produce. When heating these jars, set the cooking time for 30 seconds to 1 minute at a time, and frequently stir the contents to help prevent pressure from building up. Stirring also helps the food heat more evenly. Never heat with the metal lid on, and always use oven mitts and pads when removing the jars to prevent burns.

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Featured Image Credit: Reece with a C, Shutterstock


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