Is Borosilicate Glass Microwave-Safe
What to know

Is Borosilicate Glass Microwave-Safe?

Various materials offer safeness against microwave rays or radiation. They don’t burst into flame or bring up their temperature to the point of becoming superheated. You have microwave-safe plastic, ceramic, and glass dishes available that you can use in order to reheat or cook food.

However, what about borosilicate glass? Indeed, is borosilicate glass microwave safe? How microwave-safe is borosilicate glass exactly?

Is Borosilicate Glass Microwave-Safe?

Many borosilicate glass dishware, dinnerware, or bakeware will declare that their product has dishwasher-safe and microwave-safe properties. Meanwhile, the borosilicate material also prides itself on being stain-resistant and non-porous for good measure.

You can use mixing bowls, plates, bowls, mugs, and so forth made of quality glass, and don’t worry about the dangers of thermal shock. Thermal shock happens when a super-hot dish gets placed in a sink full of cold water and it shatters from the sudden temperature drop.

Because borosilicate glass has a thermal resistance and microwave transparency—the microwave rays just pass through the material—it won’t absorb the microwave energy and will resist the hotness of the food being reheated at the same time.

Borosilicate Glass
Borosilicate Glass

What is Borosilicate Glass Anyway?

Borosilicate glass gets its name by containing boron trioxide, which enables for a low thermal expansion coefficient. Long story short, it’s especially resistant against thermal shock. It won’t crack under pressure or extreme temperature changes on top of being resistant against heat or cold.

When in regular use, you can heat up dishes or mugs made of the material from 392°F to 446°F. When used sparingly or from time to time, the glass can survive up to 752°F. In other words, the more regularly you heat it up above its limit of 446°F, the likelier it could break.

Most anything you cook in the oven, including the microwave oven, won’t require anything beyond 446°F anyway. It’s not like you’re making a sword or cutlery as well as baking a clay pot.

Is Borosilicate Glass Better Than Regular Glass?

Borosilicate glass, unlike regular glass, won’t crack under extreme temperature changes or fall victim to thermal shock. The durability of this material has made it the glassware material of choice for wineries, laboratories, and high-end restaurants.

15 percent of boron trioxide can be found in borosilicate glass. This magical ingredient changes glass behavior and properties, making it more resistant to thermal shock specifically. This enables the glass to resist extreme temperature changes measured by the “Coefficient of Thermal Expansion”.

The Thermal Expansion Coefficient measures the rate of glass expansion when exposed to heat as well as changes in temperature.

Straight from the Freezer to Oven or Microwave

Because of borosilicate glass’s extreme temperature change resistance and thermal shock resistance, you can place it straight from the freezer to the oven rack without it cracking from the sudden change from coldness to hotness.

You won’t have to place your food in a separate glass in order to microwave or defrost it. You can pour boiling hot water unto the glass if you wish to steep coffee or tea without worrying about it shattering or cracking due to the sudden change in temperature.

Furthermore, the glass also features resistance against acid and chemical degradation. Nothing will seep into your water care of the glass since it’s nonporous as well.

The Many Benefits of Borosilicate Glass

You can always safely drink from a borosilicate glass container, cup, or mug. Nothing from any previous drinks you’ve consumed should seep into the water as long as you washed the container nicely since it’s a nonporous container with acid degradation resistance.

On top of being microwave-safe, borosilicate glass mugs and dishes can also be safely washed inside your dishwasher. You can even leave it out in the sun or store hot liquids on it without worry. Like ceramic, it resists the temperature changes possible inside the microwave.

A borosilicate glass bottle, dish, bowl, or mug won’t release harmful toxins into the liquid you’re consuming when it’s heated up, in contrast to plastic water bottles or stainless steel mugs.

What’s the Difference of Borosilicate Glass and Soda-Lime Glass?

Most companies choose the more affordable soda-lime materials when making their dinnerware or drinkware because of its cheaper price and ready availability. Soda-lime accounts for 90 percent of manufactured glass across the globe.

It’s also utilized for items such as glass windows, beverage glasses, vases, pottery, and furniture. However, this glass can succumb to thermal shock and it doesn’t handle extreme hot temperature changes as superbly as borosilicate glass.

At normal temperatures though, it’s perfectly durable and serviceable. We’ve derived the name “soda-lime” from its key ingredients. It’s composed of 9 percent lime (calcium oxide), 15 percent soda (sodium oxide), and 69 percent silica (silicon dioxide).

The Superiority of Borosilicate Glass

Soda-lime glass doubles the Coefficient of Thermal Expansion of borosilicate glass. This means it expands more than twice as quickly due to heat exposure compared to its borosilicate counterpart, resulting in breakage and shattering that borosilicate glass normally resists.

Meanwhile, borosilicate glass offers 80 percent of silicon dioxide in its composition compared to soda-lime glass’s 69 percent of silicon dioxide. The higher silicon percentage also explains why borosilicate resists fractures better than soda-lime.

The Maximum Thermal Shock Range and Nuclear Waste

Borosilicate glass has a maximum thermal shock range of 340°F (170°C). This is the temperature difference it could withstand before breaking. This is the reason why you can take borosilicate glass and Pyrex bakeware out of the oven and then run cold water over it without thermal shock fracturing.

Borosilicate glass offers so much resistance against chemical degradation that it could even store nuclear waste safely without undergoing radiation degradation like other materials. In contrast, soda-lime glass can barely be called microwave-safe.

At the End of the Day

Not all glass is created equal. Borosilicate glass can be considered “Glass+” or “Glass 2.0” in the way it’s able to resist thermal shock, matter expansion in the coldness of your freezer, and even blunt-force impacts.

You can heat borosilicate glass because it features both cold resistance and heat resistance. This makes it good bakeware and microwaveable material at the same time. You can also bring dishes made of this glass from the freezer to the oven or microwave with no issues.


  1. What Is Borosilicate Glass And Why Is It Better Than Regular Glass?“,, Retrieved October 7, 2021

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