Can You Microwave Glass? How Safe is it?

Can you microwave glass? It’s a common question that people have, and the answer is yes – you can microwave glass. However, there are some things you need to know before doing so.

In this blog post, we’ll cover why glass is a convenient material for food storage and heating, and we’ll also provide some tips on how to safely microwave glass containers. Read on to learn more!

What is Glass?

Glass is a material that is made by melting silica, a type of sand comprised of smalls grains of quartz crystals, and other materials in a furnace at a very high temperature- around 3090 degrees Fahrenheit. The molten material is then poured into a mold, where it is allowed to cool and harden. After being heated and then cooled, the material turns into a completely different material, what we know as glass. Glass can be made into different shapes and sizes, and can be colored or clear.

Many manufacturers are creating their glass dishware with what’s called tempered glass. Glass can undergo a tempering process in which it’s heated and cooled very rapidly during the production stage. This strengthens the glass and helps it handle thermal shock better. Pyrex is a great example of this. It’s specifically designed to handle extreme temperature changes. Tempered glass is also stronger than regular glass, and is less likely to shatter if it breaks.

Can You Microwave Glass?

Most glass is microwave-safe so yes, you can microwave it!

Unless specifically noted by the manufacturer, do NOT microwave:

  • Colored glassware
  • Glass with metallic trim
  • Glass-ceramic

How to Test if Glass is Microwave-Safe

Whenever you are unsure if glass is microwave-safe or not, you can do your test in your microwave. Just follow the below steps!

Step 1: Find a dish you know for a fact IS microwave-safe. It can be a Pyrex measuring cup or even a Tupperware container.

Step 2: Pour water in the microwave-safe dish halfway full. Leave some room at the top.

Step 3: Place the microwave-safe dish in the microwave alongside the dish in question. Do not pour anything in the dish you are testing. Leave it empty.

Step 4: Microwave on high for one minute.

Step 5: After one minute, open the microwave and feel the empty dish you are testing.

If the dish is hot, it is not microwave safe. If the dish is cool or slightly warm, it is microwave-safe.

How to Microwave Glass

Here is a step-by-step guide on microwaving glass.

Note: Do not directly microwave glass dishes from the refrigerator and freezer. Most glass can’t handle the thermal shock of extreme temperature changes. Unless it’s a brand, like Pyrex, which is well known for creating tempered glass products that are designed for sudden changes in temperatures.

Step 1: Put food in glass dish. A thin even layer is best. Microwaves are known for not heating up food evenly.

Step 2: Cover the dish with saran wrap. Leave one corner vented about an inch though. This will keep the food moist and not dry out. The microwave works to heat up food by removing the water moisture.

Step 3: Use a medium-high heat setting on the microwave. We recommend this so you can keep an eye on your food and it doesn’t burn or overheat!

Step 4: Microwave in 30 second intervals. This might not seem like a lot, but the microwave heats up food faster than the oven! This will also allow you to observe it while cooking.

Step 5: (Optional) Stir if your food is liquid or isn’t fully solid. This will allow the heat to distribute more evenly.

Step 6: Microwave up to 5 minutes. Anymore and the glass may not be able to handle it.

Step 7: Take out and enjoy!

Dos and Don’ts for Microwaving Glass

If you do decide to microwave glass, there are a few things you should keep in mind: 

  • Do place the glass on a microwavable safe plate or coaster. This will help distribute the heat evenly and prevent the glass from shattering. 
  • Do use a low setting if possible. The lower the setting, the less likely the glass is to shatter. 
  • Do heat the glass for short intervals of time (no more than 30 seconds at a time). Allowing the glass to cool down between intervals will also help prevent shattering. 
  • Don’t put metal objects in the microwave with the glass. Metal objects can cause sparks which can break the glass. This includes metallic rimmed glass.
  • Don’t try to reheat an already heated piece of glass. Once the glass has been heated, it becomes much more fragile and more likely to break. Example, glass that has recently been in the oven.
  • Don’t use cold water to cool down a hot piece of glass. Sudden temperature changes can cause the glass to shatter. Instead, allow the piece of glass to cool down gradually on its own or run it under lukewarm water. 

Can You Microwave Cold Glass?

You should not microwave cold glass, unless you are using Pyrex. Pyrex uses a special tempered glass designed to withstand extreme temperature changes.

Transfer food from a cold glass dish to a room temperature one.

FAQs for Can You Microwave Glass

How Long Can You Microwave Glass?

Glass will not melt unless it reaches 900 degrees Fahrenheit, so it’s unlikely to melt in the microwave. However, glass can still shatter and break when exposed to too much heat.

Try to keep your glass dish in the microwave no longer than 5 minutes total. But you don’t want to keep your glass dish in that long at one time. Glass still needs to be microwaved in short intervals of 30 seconds.

Can You Microwave Glass Pyrex?

Pyrex is one of the safest types of glass to microwave! Pyrex is made from a specific tempered glass that is designed to withstand extreme temperature changes. Glass Pyrex is less likely to break or shatter and is extremely heat resistant.

Is IKEA Glass Microwave-Safe?

IKEA glass is microwave-safe up to 212 degrees Fahrenheit according to the manufacturer’s guidelines! When in doubt, it’s always best to go to the manufacturer’s website and see what they have to say. They will be your best answer.

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