Can You Put Glass in the Microwave?

Appliance Express
October 2, 2023
Microwave Repair

Microwaves are a convenient appliance that can heat up food in a matter of seconds. With its widespread use, people know a lot of general facts about microwaves, but they might wonder whether they can put glass in the microwave or not. 

Glass makes for an excellent food-storage material as it is durable, easy to clean, and doesn’t absorb flavors or odors. 

However, before putting glassware in the microwave, you must consider certain factors. In this blog post, we will look at whether it’s safe to use glass in the microwave and the precautions you should take.

Can you put glass in the microwave?

Glassware comes in various forms, including oven-safe and microwave-safe options. If you’re unsure about the kind of glassware you own, it’s best to take a minute and look at the label or manufacturer’s instructions. If the label states that the glass is microwave-safe, you’re good to go. 

To tell if the glass is microwave-safe, you need to inspect the product for any labels or symbols indicating that it’s safe for use in a microwave. Many manufacturers will include this information on the bottom of the glassware.

However, if the label says not to microwave or does not say whether the glass is microwavable, it’s better to err on the side of caution and not use it in the microwave. Heating glass that’s not labeled microwave-safe can cause it to shatter or break, creating a mess and, even worse, harmful shards.

Non-microwavable glass can break in the microwave due to thermal shock. When you heat something in the microwave, the energy heats up the molecules in the food or liquid. This can cause the temperature of the item you’re heating to rise very quickly.

If the glass isn’t microwave-safe, it may not be able to withstand these rapid changes in temperature. The outer layer of the glass can heat up and expand much faster than the inner layer, causing stress that leads to breakage. This phenomenon is known as thermal shock.

When using glassware in the microwave, make sure that it doesn’t have any metallic trim or embellishments. Metal is a conductor of electricity, and when put in a microwave, it can lead to sparking and accidents. The microwaves generated by the microwave affect the surfaces of the material they heat. This is fine on smooth surfaces, but on edges, the electrons can accumulate and create a charge of voltage. To us, that looks like sparks or arcing.

Additionally, some dyes or pigments can react to the heat generated by microwaves, causing the glass to crack or shatter due to thermal shock. This is especially true if the dye is only on the surface of the glass, creating a temperature difference between the colored and clear parts of the glass. It’s also worth noting that even if a dye is safe for microwave use, it can still fade over time with repeated exposure to microwaves. 

Also, avoid putting glassware with any damage, such as scratches or cracks, into the microwave. Cracks or chips in the glass, even those invisible to the naked eye, can cause the container to explode in the microwave. Again, since microwaves are altering the surface electrons of the glass, they can accumulate in the cracks and chips and weaken the glass until it shatters. The heat can also build quickly, making the glass flex and burst along the cracks or chips.

If you decide to use glassware in the microwave, it’s recommended that you cover it using a microwave-safe lid or wrap it with a microwave-safe plastic wrap. Doing this can help prevent the glass from cracking or breaking. The rim is more vulnerable to cracking since the glass is typically thinner there. Additionally, covering the container helps retain the moisture in the food and speeds up the cooking process.

Also, keep the cooking time under five minutes to prevent any cracking or chipping.

The thickness of the glassware can also determine its capacity to handle the microwave’s heat. Thin glassware heats up faster, making it more prone to shattering. In contrast, thicker glassware can handle the microwave’s heat for an extended period without any issues. Therefore, it’s best to choose heavier glassware or a container that’s specifically labeled microwave-safe.

You should also avoid heating thinner glass, like cups or mugs, in the microwave.

If you really want to test whether a glass is microwavable or not, you can run the following test:

Pour a cup of cold water into your glass container and place it in the microwave for a duration of 1 to 2 minutes. 

Afterward, check its temperature. If the glass feels hot, it’s not suitable for microwave use. However, if it’s just mildly warm or remains cool, yet the water inside is hot, then the dish is probably safe for the microwave.

Bear in mind that delicate glass may shatter during this microwave examination. Always exercise caution.

How does a microwave work?

A microwave oven works by producing microwaves through a device inside called a magnetron. These microwaves are then pushed into the oven’s interior, where they bounce around off the walls. The food placed inside the oven absorbs these microwaves.

Microwaves specifically target water molecules in food. As these microwaves enter the food, they make the water molecules vibrate. This vibration generates heat through a process called dielectric heating. As the water heats up, so too does your food.

Microwaves can still affect substances without water in them, like glass or ceramic, to varying degrees. The temperatures created by microwaves are also a factor in determining whether a material is microwave-safe or not.

Glassware is an excellent choice for microwave cooking as long as it’s labeled microwave-safe. However, it’s essential to consider the factors covered in this blog post before using it, such as the glassware’s thickness, condition, and the presence of metallic embellishments. By following manufacturer recommendations and safety tips, you can use your glassware in the microwave without any mishaps. Remember, safety should always come first.


Leave a Reply