Borosilicate glass tea pot and tea cups

You may think that glass is glass. However, there is actually a range of types of glass with various properties. One of these is Borosilicate glass, whose unique composition makes it suitable for a range of special uses, from cookware to lab equipment.

So what is Borosilicate glass exactly? Let’s start there.

What is borosilicate glass?

Borosilicate glass contains boron trioxide. This component creates a glass that, in technical terms, has a low coefficient of thermal expansion.

What this means in technical terms is that, unlike regular glass, borosilicate glass will not crack with extreme temperature changes. This makes it highly durable, and ideal for making tableware and cookware, for example, borosilicate cups capable of accommodating boiling water, or oven dishes that can withstand high temperatures.

In fact, borosilicate glass is so tough that it’s even used to store nuclear waste! It’s highly durable meaning it is not only resistant to cracking and shattering but can also be molded into complex shapes.

borosilicate drinking straw
Drinking straw with a turtle made of borosilicate glass

This kind of glass is non-porous, so chemicals won’t leach into the glass or vice-versa and will be resistant to acid erosion.

Because of these properties, borosilicate glass has been used in laboratories and the industrial sector for many years. It is also a popular choice for making premium bakeware, glasses, and other kitchenware.

More recently, borosilicate has become a common choice to make reusable bottles for eco-conscious consumers. This material is ideal for this purpose as it is highly durable, dishwashable, and won’t leave a metallic taste in your mouth or leach chemicals into your water, unlike some plastic bottles.

The main uses of borosilicate glass are:

  • Cookware – Pyrex first made borosilicate famous at a household level in the early 20th century with their borosilicate glass oven dishes and other cookware.
  • Water bottles and jugs – More durable and versatile than regular (soda-lime) glass, borosilicate glass is a strong and sustainable alternative to plastic.
  • Wine glasses – Some high-quality wine glasses are made with borosilicate glass for its strength and durability.
  • Laboratory equipment – chemistry labs and other research facilities use borosilicate glass because it is non-porous, and resistant to chemicals, acid, and extreme temperature changes.
  • Industry – Manufactures use borosilicate as a heavy-duty alternative to soda-lime glass in industrial machinery, such as for viewing windows and console panels.

What is borosilicate glass made from?

Borosilicate glass can be made in a few different ways, including moulding, tube drawing, and floating.

It contains around 15% boron trioxide, which gives the glass distinct properties. Most notably, it makes glass resistant to thermal shocks, meaning it can withstand extreme temperature changes.

This is connected to the “Coefficient of Thermal Expansion” – the rate that a material expands when exposed to heat. For example, when you put boiling hot water in a cold glass cup, the glass expands rapidly and will probably crack or shatter.

On the other hand, if you expose borosilicate glass to the same rapid change in temperature, the glass will remain intact.

You can even take a borosilicate glass dish from the freezer and put it into a hot oven without any problems! Borosilicate glass can tolerate a change in temperature of up to 320 degrees Fahrenheit (this is called the maximum thermal shock range).

Is borosilicate glass better than other types of glass?

Borosilicate glass typically has a composition of around 13-15% boron trioxide, 2-3% aluminum oxide, 4% sodium oxide, and 80% silica.

This gives borosilicate the following properties:

  • Thermo-resistantance (it can withstand extreme temperature changes)
  • Highly durable
  • Malleable
  • Resistant to acid
  • Non-porous (won’t leach or absorb chemicals)

This special type of glass is manufactured at very high temperatures, higher than soda-lime glass. Along with its composition, this helps to make borosilicate very durable and heat-resistant.

In essence, this type of glass has the advantages of both regular glass and plastic without the drawbacks of either: it is as strong and durable as plastic, while being inert, non-porous, and environmentally-friendly like glass.

Borosilicate glass is more expensive, but it will last you a long time, so you’ll find it’s worth the investment.

It’s better for you

Like other types of glass, borosilicate glass is completely inert and non-toxic. This means it is 100% safe to use as cookware and tableware.

Take reusable plastic bottles, for example. These are often made from BPA plastic and can leach BPAs into your water with a range of potential health implications, including possible links to increased blood pressure, type 2 diabetes, and cardiovascular disease, as well as impacts on the brain and prostate gland, particularly in infants and children.

Borosilicate glass is BPA-free and completely non-toxic.

However, it’s important to check the composition of all components in the borosilicate product you buy. If it is pure borosilicate, you can be assured that it is 100% safe, but if it contains other parts made from plastic, metal or other types of glass, be sure to check whether these are safe.

For example, this PROBTTL 32 Oz borosilicate glass bottle has a bamboo lid and silicone sleeve – so no toxic plastics will touch your water!

Your food and drink will taste better

Borosilicate glass is 100% inert, like other forms of glass. This means it doesn’t leach chemicals or metals, and your food or drink will taste better in a borosilicate glass, bottle, or oven dish.

It’s better for the environment

Borosilicate glass offers a sustainable alternative to single-use plastics, helping you to live a more eco-friendly lifestyle. Safe, non-toxic, and highly durable, borosilicate makes the perfect reusable water bottle, so you’ll never buy bottled water again!

Even better, the thermo-resistant properties of borosilicate glass mean that you could use it for both hot and cold liquids.

What’s the difference between borosilicate glass and soda-lime glass?

Soda-lime glass is the most common type of glass used today, used to make everything from drinking glasses to window panes. In fact, around 90% of glass manufactured globally is soda-lime glass.

It’s so popular because it’s readily available and one of the cheapest forms of glass to produce, but it is not as durable as borosilicate glass. Soda-lime glass does not contain any boron trioxide: its composition is 69% silica (silicon dioxide), 15% soda (sodium oxide), and 9% lime (calcium oxide).

This compares to 13-15% boron trioxide, 2-3% aluminum oxide, 4% sodium oxide, and 80% silica in Borosilicate glass.

Compound Borosilicate Glass – % contentSoda-Lime Glass – % content
Boron trioxide13% – 15%
Silicon dioxide80%69%
Sodium oxide4%15%
Calcium oxide9%
Aluminum oxide2% – 3%

This means that although it is relatively durable, soda-lime glass is not resistant to shock or changes in temperature. Soda-lime glass has around double the coefficient of thermal expansion of borosilicate glass, so expands twice as fast when exposed to heat and is much more likely to break.

Furthermore, because borosilicate glass has a higher silica content, it is stronger and more resistant to breakage.

Is borosilicate glass the same as Pyrex?

Borosilicate glass is not the same as Pyrex – at least not anymore. Pyrex bakeware was made from borosilicate glass when it was first released in 1915, and the terms “Pyrex” and “borosilicate glass” became interchangeable.

However, these days not all of Pyrex’s products are made from borosilicate glass. The brand switched to cheaper tempered glass years ago, and it’s difficult to know which items are made from borosilicate.

Pyrex measuring cups
Two Pyrex measuring cups: one manufactured by Corning (right) with borosilicate glass, and one by Instant Brands (left) using soda-lime glass

Pyrex has been made with tempered glass instead of borosilicate glass for decades.

The company which makes Pyrex, Corelle Brands, told the New York Times they’ve been producing tempered glass since the 1950s, though they wouldn’t say when they switched exactly.

Tempered glass is more durable and better at withstanding thermal shock than soda-lime glass but not as resilient as borosilicate glass. Furthermore, when it breaks, it’s likely to shatter rather than crack.

Why you should look out for Borosilicate glass

With Borosilicate glass bottles, jugs, and bakeware experiencing a resurgence in popularity in recent years, we’ve seen this become something of a buzzword as of late. There are many good reasons for this – this kind of glass is highly durable, thermo-resistant, environmentally friendly, safe, and non-toxic.

Although Borosilicate glass costs more than plastic or other types of glass, these products last forever, so your investment will pay off in the long run. Just make sure you buy a genuine Borosilicate glass product, as tempered glass and soda-lime glass do not have the same properties and benefits!

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