Can you Microwave Glass? [Detailed Answer with Safety Precautions]

Can you Microwave Glass?Almost every home today owns a microwave oven due to its efficiency in cooking and heating your food. It’s fast and easy.

For this reason, you may be spoiled by the convenience and commonness of the microwave that you fail to acknowledge its potential hazards. Unsafe glassware may explode in the microwave.

Can you microwave glass? Yes, you can microwave glass but with precautions since not all glassware is safe. Some may shutter or break from the rapid microwave temperature changes.

The safe glassware for the microwave is imprinted with a certified logo at the bottom of the glass dish. However, if your glass dish is not impressed with a certified safe logo, it doesn’t imply that it will break when you place it in your microwave oven.

Reasons Why Non-Microwave-Safe Glass Dish May Shatter

1. Trapped Air

The non-microwave-safe dish may shatter due to trapped tiny air bubbles during the manufacturing of the glass. The air bubbles expand when the glass is under microwave oven heating; hence, the glass shatters if the bubbles grow to a particular extent.

If the glass is colored, search for a microwave-safe logo before placing it in your microwave oven.

2. Metal Trimmed Glass

Metals are not microwaving safe; thus, they spark, causing the glass to break when placed in a microwave. A microwave is an electromagnetic form of radiation created by a magnetron device.

The walls and door of the microwave oven have metals for safety measures that ensure the microwaves don’t escape and cook other objects.

These metals in the microwave oven reflect the microwaves focusing them on the cooking food. Then specific molecules in the food absorb the microwaves.

On the other hand, metals like knives, spoons, and forks are excellent conductors of electricity since they have a lot of free electrons. Hence, when a microwave hits a metal object, it gets reflected, which may cause problems.

Additionally, if there is no sufficient material lining the oven to absorb all the reflected microwaves, arcing between the metallic object and some parts of the microwave will occur. This can damage the oven by destroying the magnetron, starting a fire, or damaging the sensitive electrical components.

How to Test a Microwave Safe Glass

Step one: Take a microwave-safe labeled cup and fill it with three-quarters full of water.

Step two: Grasp the glass dish you intend to test whether it’s labeled microwave-safe or not. Place the cup and the dish side by side inside the microwave. Put the cup over the glass dish if the space is not enough.

Step three: Microwave the cup and the glass dish for a maximum of 30 seconds. Then perform the test by touching and comparing the results.

Step four: If the glass dish turns out to be warm and the water in the cup labeled microwave-safe is cold, then the container absorbs much heat meaning the glass dish isn’t microwave safe.

Step five: If the water in the cup is hot and the plate is cold, then the test dish isn’t absorbing heat, meaning it’s safe for use in a microwave.

Safety Precautions to Microwave Glass

Glass containers, dishes, and cookware are not equally created. Therefore, before you start putting any glass container in your microwave, here are some safety and heating tips to consider.

1. Use Only Top-Quality Glass Dishes From Reputable Brands

Always check if the manufacturer’s glass container, cup, or plate has a microwave-safe logo. If it does not have a microwave-safe symbol, test it for safety first before placing it in your microwaveExamine the Colored Glass If It’s Microwave Safe

Can you Microwave Glass?When using colored glassware, ascertain that it’s microwave safe. Or else the dye applied can get into your food, making it unsafe to consume.


2. Avoid Overheating Glass Containers When In the Microwave

Overheating glass containers can cause damages or accidents to the appliances or cookware you are using. Use three minutes intervals and stir your food in-between the durations.

3. Don’t overcrowd food

Filling a dish with food to the top reduces the microwave’s ability to heat food. Food gets unevenly heated, resulting in cold and hot.

4. Reheat Food to the Correct Internal Temperature

Reheated foods should be microwaved till they pass the temperature danger belt. Again reheated food must be heated to the least internal temperature of 74bdegrees Celsius or 165 degrees Fahrenheit.

5. Microwave Similar Foods

Food products vary in technique, temperature, and cooking time; hence it’s best to put similar foods in the glassware for microwaving. Heating dissimilar foods will result in off textures and flavors.

What Happens When You Place Glassware In The Microwave?

Can you Microwave Glass?It is crucial to determine its glass type before putting it in the oven. If its heat resistant glassware, you can place it in the oven as you follow the safety measures. However, ordinary and toughened glass containers should be set for a short heating period in the range, at a maximum of three minutes only.

Otherwise, if left under high temperature, an explosion of the glass can occur. Delicate glasses can crack when exposed to extreme heat. Curved and crystal glass products can break when heating oily foods due to the unequal thickness of materials.

Furthermore, sugar and fat-rich foods have high heating temperatures than water-based foods. Therefore you should microwave foods high in sugar and fat cautiously.

Things You Should Know About Placing Glass in a Microwave Oven

Should Have a Microwave-Safe Symbol

Glasses with a microwave-safe logo are best for cooking or reheating food in the oven. Although some lack the certified safety logo, they can be safe since glasses don’t leach chemicals into the food plastics does.

The absence of a safety label means they are delicate and of poor quality. However, it doesn’t mean they’ll explode when microwaved. But unfortunately, they might crack when removed from the oven.

They Are Prone To Thermodynamic Transition

They could also crack when the cold and hot thermodynamic transition occurs too quickly. Metal sparks produced by the microwave destroy fragile glasses. However, the glassware may not catch fire, but it could shatter due to the power surge.

Can Break Easily

Again it would be best to avoid heating cheap glasses since they break under high temperatures and aren’t heat resistant. Ordinary glasses may break by putting hot drinks or food in them; however, it’s far better to use glass than Styrofoam, cardboard, or plastic to heat food.

Is it Safe to Microwave Glass Tupperware?

No, Tupperware is generally used to store food; therefore though it is glass, you shouldn’t assume that you can microwave it safely. Instead, you should always check underneath the container for a label that shows it’s microwave safe.

On the other hand, microwaving in plastics is associated with leaking or transferring chemicals into the food. Therefore, it’s essential to note that a plastic container with the logo “microwave safe” says it won’t melt.

How can you tell a Microwave Safe Container?

Here are some features to check if a container is microwave-safe or not

  • Most containers have a symbol or label at the bottom.
  • The microwave-safe items are always labeled with wavy lines underneath the container.
  • Another indicator is CPET for microwave-safe items
  • APET symbols show that an item is not microwaving safe. They are used in recyclable and for packaging food; hence, they are not safe for cooking or reheating food.
  • Paper products like paper plates or paper cups should not be placed in the microwave because some are sealed, glued, or coated; thus, the additives can leak into your food
  • Styrofoam or polystyrene is not microwaving safe because it melts from the heat; thus, it’s mainly used for its cording properties. They keep the food warm; however, reheating them in the microwave oven can be dangerous.
  • “PP” symbol inside a triangle and a number “5” indicates that the container is microwave safe.

Faqs About Microwaving Glass

Can cold glass go in the microwave?

No, irrespective of what the glass is made of, whether synthetic or natural glassware, you cannot microwave it in a cold state. Therefore microwaving cold drinks from the freezer is a big no. If you place a cold glass container into the microwave and switch it on, the highest probability is shattering or breaking. This is because of the different temperatures of the microwave and glass containers.

Can you warm the glass up in the microwave?

No, it is not safe to heat glass in the microwave, mainly if it’s empty. And because the bubbles will expand during heating, this may cause the glass to shatter or even crack. However, it depends if the glass is microwave safe. Check for the safety symbol at the bottom of the glass before placing it in the microwave.

Can you microwave cold bowls?

No, when you place a cold bowl in the oven, it may explode or crack; this depends on how cool the bowl is when it’s put in the microwave. Refrigerated bowls are ok to put in the microwave; however, avoid placing them until the frost is melted if the bowl is frosty.

Is it ok to put a cold glass dish in the oven?

Yes, putting a cold glass dish in the oven is ok, but you have to apply precaution to ensure the glass is heat-resistant. Again watch out for extreme heat differences. Sudden temperature changes could cause your glass to break. Additionally, remember that some glasses aren’t recommended to be placed in a scorching oven.

Is it wrong to heat cold glass?

No, regardless of glass being generally microwave safe, microwaving cold glass is terrible. Hence, a cold glass will shatter or break when exposed to high-temperature changes in an extreme heat microwave. Although glass is the best material for cooking since it is exceptionally durable and can withstand very high heat, it does not apply to cold glass; hence, it is not recommended to heat it.

How long can you microwave glass for?

A glass can handle a maximum of three minutes in the microwave. Allow enough time between every interval as you rotate the container, even when using microwave-safe glassware. However, microwave it for two minutes or 120 seconds when heating food because too much heat can make the glass crack or shatter, even though it has a microwave-safe symbol.

Can you microwave old Pyrex

Yes, old Pyrex is oven-friendly since it’s initially made for use in the microwave. However, some old Pyrex has patterns denoted with metallic gold leaf, and as mentioned earlier, metals cannot go in the microwave. So you have to apply caution when placing old Pyrex in the microwave.

Can I microwave a mason jar?

Yes, a mason jar can go in the microwave; however, it may not have a microwave-safe label depending on your jar’s age. Again, the rings and rids on the Mason jar have metal, making it unsafe to microwave it.


In conclusion, it’s right to say that only a microwave-safe glass can be put in the microwave, even though it’s slightly cold. But if the glass is made of synthetic and natural glass, avoid placing it directly in your oven when it’s too cool.

Additionally, always wipe the condensation with a towel to prevent the glass from shattering or breaking inside the microwave.

It’s critical to advise that tiny air pockets or exterior decorations on the glass can affect the performance leading to potential hazards if heated in the oven. Hence, it’s essential to stick to microwave-safe containers guaranteed to withstand high heat.

Check out this video for more

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top