Is Borosilicate Glass Microwave Safe?

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Microwaving leftovers or heating up a ready meal is a quick and easy way to get food on the table. But is the glass bakeware or containers you use safe for microwaving? If it’s made from borosilicate glass, the answer is a resounding yes.

Borosilicate glass is not only microwave-safe, it’s one of the most durable and versatile options for cookware. Let’s look at why borosilicate glass is ideal for microwave use and how its unique properties allow it to withstand rapid temperature changes without cracking.

What Is Borosilicate Glass?

Borosilicate glass gets its name from its main ingredients – silica (silicon dioxide) and boron trioxide. It was first developed over a century ago by German glassmaker Otto Schott.

Some key facts about borosilicate glass:

  • Contains at least 5% boron trioxide
  • Low coefficient of thermal expansion
  • Withstands thermal shock
  • High heat resistance
  • Resistant to chemical corrosion
  • Non-porous surface

The addition of boron is the key. It reduces the expansion of the glass during heating, making it highly resistant to thermal shock.

This thermal shock resistance means that it can withstand rapid temperature changes without cracking or shattering. A piece of borosilicate glass won’t crack if you take it from the freezer and place it directly in a hot oven.

Compare this to regular soda-lime glass which has a much higher coefficient of thermal expansion. It’s prone to cracking under thermal shock.

Borosilicate glass is also resistant to chemical corrosion. Its non-porous surface won’t absorb stains or flavors either.

Why Borosilicate Glass is Microwave Safe

Here are the main reasons why borosilicate glass is one of the most microwave-safe options available:

Heat Resistance

Borosilicate glass has high heat resistance, especially compared to plastics. It’s designed to be used for laboratory glassware, ovenware, and cookware.

The maximum use temperature varies by brand but is typically around 500°F. Some can withstand temperatures up to 1000°F for short periods.

This high heat tolerance makes it suitable for use in a microwave oven where localized super-heating can occur.

Thermal Shock Resistance

The thermal shock resistance of borosilicate glass prevents it from cracking when exposed to rapid temperature changes.

You can safely go from freezer to microwave or oven with borosilicate containers. This makes it very convenient for reheating leftovers.

Microwave Transparency

Borosilicate glass is transparent to microwaves. It allows them to pass through and heat the food or liquid inside directly.

Materials like metal reflect microwaves instead of absorbing them. This can create problems like arcing.

Non-Porous Surface

The non-porous surface of borosilicate glass means it will not absorb any colors, flavours or chemicals from the food being microwaved.

Is All Borosilicate Glass Microwave Safe?

The borosilicate glass needs to be of sufficient quality and thickness to be considered microwave safe.

With lower quality glassware, there is a risk of thermal fractures occurring in the glass when exposed to rapid heating. Over time, this thermal stress can weaken the glass.

High-quality borosilicate glass from reputable brands like Pyrex and Simax is designed for safe microwave use. They have stringent testing procedures to ensure their products meet specifications.

Always check the labeling to confirm if the borosilicate glassware is microwave safe or not. Don’t assume that all borosilicate products can be used in the microwave.

Advantages of Borosilicate Glass for Microwaving

Here are some of the main benefits of using borosilicate glass containers and cookware in your microwave:

  • Heat resistant – Won’t melt or leach chemicals when exposed to heat. Safer than many plastics.
  • Thermal shock resistant – Rapid temperature changes won’t cause fractures.
  • Microwave transparency – Allows microwaves to pass through and heat food.
  • Non-porous – Won’t absorb stains, flavors or odors.
  • Chemical resistance – Won’t leach chemicals into food or react.
  • Reusable – A durable option that can be used repeatedly.
  • Easy to clean – Non-porous surface just needs washing.
  • Visibility – Allows you to view the food while cooking.
  • Oven and freezer safe – Use the same container for heating, cooking, storing.

Borosilicate glass is more expensive than alternatives like plastic or ceramic. But it’s worth investing in high-quality glassware for the safety, performance and convenience it provides.

Is Pyrex Borosilicate Glass?

Pyrex is probably the most well-known brand of borosilicate glass kitchenware. The Pyrex name has become synonymous with glass baking dishes and heat-resistant glass.

Originally Pyrex glassware was made from borosilicate glass. However, many Pyrex products today are now made from tempered soda-lime glass instead.

So Pyrex is not guaranteed to be borosilicate glass anymore. You need to check the labeling and fine print.

Pyrex containers labeled as oven, freezer and microwave safe will be borosilicate glass. This original Pyrex glassware remains widely available from retailers.

The soda-lime Pyrex is more susceptible to thermal shock than the original borosilicate version. However, with proper care it can still be used for most everyday microwaving tasks.

Always refer to the manufacturer’s instructions and labeling for usage guidelines.

Is Plastic or Glass Better for Microwaving?

Glass is generally a safer choice than plastic for microwave use.

Not all plastics are created equal when it comes to heat tolerance. Some types of plastic can warp, melt, or leach chemicals when exposed to heat from microwaving. This depends on the plastic grade and composition.

With glass there is no risk of chemicals leaching, even when subjected to heat. And borosilicate glass can withstand much higher temperatures than plastics.

The risks with plastics are mainly with lower quality plasticware not designed specifically for microwave use. Any plastic containers, wraps or bags should be labeled “microwave safe”. Never microwave plastics that are cracked or damaged.

For optimal safety and performance, borosilicate glass is the best choice for microwaving.

Is Glass or Ceramic Better for Microwaving?

Both glass and ceramic cookware are safe options for use in the microwave. They have similar properties:

  • Withstand high temperatures
  • Non-porous
  • Resistant to staining and odors
  • Allow microwaves to pass through

Ceramics are opaque so you can’t view the food inside while cooking. Glass allows visibility which can be either an advantage or disadvantage.

In terms of thermal shock resistance, borosilicate glass is superior to ceramic. Good quality ceramic will work for most reheating tasks, but it can crack if subjected to rapid temperature changes.

Glass and ceramic bowls are prone to getting hot themselves during microwaving. Always use potholders to remove them afterwards.

For versatility across cooking methods, borosilicate glass has the edge over ceramic. It offers excellent thermal shock resistance plus visibility.

Is Borosilicate Glass Safe For Food?

Borosilicate glass is considered completely safe for food use. Its resistance to thermal shock makes it ideal for cooking, microwaving and food storage.

The baked-in durability and non-porous nature mean it won’t:

  • Leach chemicals into food
  • Absorb stains or odors
  • Crack from temperature changes
  • React with acidic foods

Reputable borosilicate glass brands meet FDA and EU food safety regulations. Used correctly, it’s one of the safest food container options available.

In contrast, lower quality soda-lime glass is more likely to break down over time when used for cooking applications.

How To Microwave Safely With Borosilicate Glass

To get the most out of your borosilicate microwave cookware, follow these safety tips:

  • Always refer to manufacturer’s instructions
  • Don’t use damaged or chipped containers
  • Avoid severe temperature changes
  • Use potholders to handle hot glass
  • Don’t microwave empty or when very dry
  • Remove lid to avoid pressure build-up
  • Check food temperature before consuming

Even though it’s designed to withstand thermal shock, it’s still best to avoid putting super hot glassware straight into cold water. Allow it to cool down gradually first.

With proper care, borosilicate glassware can safely be used thousands of times. It’s built to last!

Frequently Asked Questions

Can I put borosilicate glass in the oven?

Yes, borosilicate glass bakeware and containers are oven-safe. Always check the manufacturer’s recommended temp range.

Is borosilicate glass breakable?

It’s more resistant to breaks than regular glass but not unbreakable. Avoid drops, hits, or severe temperature changes.

Can I freeze borosilicate glass?

Yes, it can safely go from freezer to microwave thanks to its thermal shock resistance. Allow temperature to adjust gradually.

Can borosilicate glass go in the dishwasher?

High-quality borosilicate glass is fine for the dishwasher. Avoid drastic heating or cooling in the cycle.

Is borosilicate glass inert?

Yes, it’s chemically inert so won’t react with food or liquids. This makes it very safe for food contact.

Does borosilicate glass scratch easily?

It’s harder than regular glass so more scratch resistant. But it can still be scratched by sharp objects. Handle with care.

The Takeaway on Borosilicate Glass and Microwaving

  • Borosilicate glass is designed to be microwave, oven and freezer safe.
  • Its thermal shock resistance allows it to withstand rapid temperature changes.
  • High heat tolerance and non-porous nature also make it ideal for microwaving.
  • When sourced from quality brands, borosilicate provides safe, durable and versatile cookware.
  • With proper use, it’s one of the most convenient and safest materials for microwave cooking tasks.

So next time you need a vessel for microwaving leftovers or rapid cooking, choose borosilicate glassware and take advantage of its excellent heat-resistant properties.

By Rosie Elliott

I’m Rosie. I’m a professional chef with experience in Western, Mediterranean, and Italian cuisine. I’ve been cooking for over 15 years, and I have two daughters that keep me busy!

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