How to Tell if Pyrex Is Borosilicate?

Learn how to identify if your Pyrex is made of Borosilicate glass. Find out the best ways to tell if Pyrex is Borosilicate with helpful tips and advice.

Are you looking for a reliable glass cookware material that can withstand high temperatures?

Pyrex is a popular choice among home cooks and professional chefs alike, but it’s important to know whether the Pyrex product you’re considering is borosilicate or tempered glass.

To make sure you get the most out of your Pyrex cookware, you need to know what type of material it is and how to properly care for it.

I’ve been using Pyrex for more than 20 years as a professional chef and glassware enthusiast, and I am well-versed in all aspects of using and caring for this versatile material. In this article, I will explain how to tell if Pyrex is borosilicate, as well as provide tips on how to maintain and use it safely.

By the end of this post, you’ll have a better understanding of how to identify Pyrex products that are made with borosilicate glass, and you’ll know how to take proper care of your Pyrex cookware. So read on to learn more about the unique properties of borosilicate glass and how to get the most out of your Pyrex products.

How to Tell If Glass is Borosilicate?

How To Tell If Pyrex Is Borosilicate
How to Tell if Pyrex Is Borosilicate

If you are unsure if a piece of glassware is made from borosilicate, there are a few ways to tell.

  • One way to tell if Pyrex is borosilicate is to look for a stamp on the bottom of the dish.
  • Borosilicate dishes often have a stamp that says “Pyrex” or “Boroclass.
  • It’s also possible to evaluate a dish at home by just observing the color. When you look at the edge of a dish constructed of soda-lime glass, it will have a blueish-green color. You should not detect any color if the glass is borosilicate.
  • Also, look for the “B” symbol at the bottom of the piece. This indicates that the drink contains boron oxide and is borosilicate.
  • Another way to tell if the glass is borosilicate is by its weight. Borosilicate glasses are heavier than regular glasses because of their boron content. Finally, you can usually identify borosilicate glass by its clear, colorless appearance.

If you’re unsure whether a piece of glassware is borosilicate, it’s always best to err on caution and assume it is. This will help ensure that you don’t accidentally damage your glassware by using it in a way that it wasn’t meant to be used (for example, using regular dish soap on borosilicate dishes could cause them to crack).

Pyrex Borosilicate

Pyrex borosilicate is a strong, durable, and heat-resistant material used in various applications. It is made up of boron, oxygen, and silicon atoms, which give it its distinctive properties. German chemist Otto Schott developed this type of glass in the early 20th century.

It was created for use in scientific laboratories, as it could withstand high temperatures and pressures. Today, Pyrex borosilicate is still widely used in labs, but it has also become a popular material for making cookware, bakeware, and even jewelry. In addition, Pyrex borosilicate is prized for its strength and durability.

It can withstand temperatures up to 500 degrees Celsius (932 degrees Fahrenheit), making it ideal for use in ovens and microwaves. Additionally, this type of glass is highly resistant to thermal shock, meaning it won’t break if suddenly exposed to extreme changes in temperature (such as from hot to cold). However, one downside of Pyrex borosilicate is that it can be challenging to work with.

However, experienced artisans and craftsmen have learned how to cut, shape and sand this rigid material into beautiful pieces of art or functional items like cookware.

Borosilicate Glass Cookware

Borosilicate glass cookware is a type of glass that is designed for cooking. It is made of borosilicate, a material resistant to heat and chemical damage. Borosilicate cookware is available in various shapes and sizes and can be used for cooking and serving food.

Borosilicate glass cookware has many benefits over other types of cookware. It is non-porous, so it does not absorb flavors or smells from food. Borosilicate glass is also highly resistant to thermal shock, meaning it can withstand sudden changes in temperature without shattering.

This makes it ideal for use in the oven or on the stovetop. Borosilicate glass cookware is also easy to clean and care for. It can be washed by hand or in the dishwasher and does not require special cleaners or treatments.

When properly cared for, borosilicate cookware will last for many years.

Borosilicate Glass Vs. Pyrex

There are many types of glass, but two of the most popular are borosilicate glass and Pyrex. Both have their unique properties and uses. So, which one is right for you?

Borosilicate glass is known for its durability and resistance to thermal shock. In addition, it can withstand sudden temperature changes better than other types of glass. That makes it a good choice for cookware and bakeware used in the oven or on the stovetop.

Pyrex is made from a glass type containing silica and boric oxide. This combination gives it a higher melting point than regular glass. Pyrex is often used for storage containers, baking dishes, and laboratory equipment because it can withstand high temperatures without breaking.

Pyrex Borosilicate Vs. Soda Lime

There are two main types of Pyrex – borosilicate and soda lime.

Both have pros and cons, so it’s essential to know the difference before making a purchase.

Borosilicate Pyrex is made with boric oxide, which makes it more heat resistant than soda lime Pyrex.

  • It can also withstand sudden temperature changes better than soda lime, making it ideal for use in the oven or stovetop. However, borosilicate is more expensive and can be harder to find than soda lime.
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Soda lime Pyrex is made with sodium carbonate and calcium oxide.

  • It’s less heat resistant than borosilicate but can withstand temperatures up to 350 degrees Fahrenheit. Soda lime is also cheaper and more widely available than borosilicate.

How Do You Test for Borosilicate Glass?

There are several ways to test for borosilicate glass:

  1. Thermal shock test: Put some ice cubes inside the glass and wait until the glass is cold to the touch, then pour boiling water on the outside. Borosilicate glass will not crack, while soda-lime glass will[1][2].
  2. Refractive index test: Borosilicate glass can be identified by its refractive index of 1.474. By immersing the glass in a container of a liquid of similar refractive index, the glass will disappear. Such liquids are mineral oil, dry benzene-methanol mixture, and anhydrous glycerol[3].
  3. Chemical composition: Borosilicate glass typically consists of around 81% silicon dioxide (SiO2) and 13% boron trioxide (B2O3) with lesser concentrations of sodium oxide and aluminum oxide[4].

How Do You Tell the Difference Between Old And New Pyrex?

When it comes to Pyrex, there are three main ways to tell the difference between old and new. The first is by looking at the bottom of the dish. If it has a raised design, then it is most likely old.

If the bottom is smooth, then it is probably new. The second way to tell is by looking at the color. New Pyrex is usually clear or white, while old Pyrex often has a blue tint.

The last way to tell the difference is by feeling the weight of the dish. Old Pyrex tends to be heavier than new Pyrex because it was made with thicker glass.

Old Pyrex vs. New Pyrex: Which is better?

This is a question that many people have when they are looking to buy new Pyrex cookware. However, there are a few things that you should consider when making your decision.

Here are some differences between each option:

Old Pyrex:

  • It is made of borosilicate glass, known for its durability and resistance to thermal shock. This means it can withstand high temperatures and sudden changes in temperature without breaking.
  • It has a smooth surface that makes it easy to clean.
  • It is oven-safe, microwave-safe, dishwasher-safe and freezer-safe. (You might be interested in Can You Put Pyrex On Stovetop?)

New Pyrex:

  • It has a nonstick surface that makes it easy to clean.
  • It can withstand temperatures up to 450 degrees Fahrenheit (232 degrees Celsius).
  • It can be used in microwaves, but it’s not oven or broiler safe. Both types of glass are safe for use in your kitchen as long as you follow proper care instructions: Wash them by hand with warm water and mild detergent.

What Does Borosilicate Glass Feel Like?

Borosilicate glass has a smooth, silky feel to it. It’s solid and durable yet lightweight and easy to work with. When heated, it maintains its shape well and doesn’t expand or contract like other types of glass.

This makes it ideal for ovens, cookware, and scientific lab equipment.

Final Thoughts

You will need to look for a few specific things to tell if your Pyrex is borosilicate. First, check to see if the bottom of the dish has a raised “B” or “BSi” symbol. This indicates that the dish is made of borosilicate glass.

You can also try holding the dish to a light source and looking at it closely. If you see tiny air bubbles throughout the glass, your Pyrex is made of borosilicate. Finally, borosilicate glass is typically heavier than other types of glass, so if you pick up a dish and it feels cumbersome for its size, this is likely another sign that it is made of borosilicate.


How to Tell if Pyrex Is Vintage?

Use the glass markings, stamps, and logos on the pieces themselves to identify when the glass was produced. A glass item’s quality is dependent upon many factors, and age is one of them. There are different methods for testing an item’s age: using the markings on the piece or through testing to determine its boron content, which can then be compared with known data for similar pieces. The two primary types of pyrex are translucent and opaque. Translucent pyrex can be identified by a little T inside a diamond etched onto its base.

How do I know if I have borosilicate glass?

There are several ways to determine if glass is borosilicate:
1. Look at the physical appearance of the glassware, including its shape and color. True borosilicate glass will be very thin, while cheaper alternatives tend to have thicker walls.
2. Check the refractive index of the glass. Borosilicate glass has a refractive index of 1.474, which can be tested by immersing the glass in a container of a liquid of similar refractive index, such as mineral oil or dry.
3. Measure the density of the glass using a water bath.
4. Look at a thick layer of the glass (e.g. along the sides). Soda-lime glass has a green-blue tint, while borosilicate glass is more yellow.
5. Borosilicate glass is made by mixing 70-80% silica sand with boron trioxide. When heated, boron trioxide absorbs massive amounts of heat before crystallizing into a glass. However, just looking at it, you might not be able to tell the difference between borosilicate glass and regular glass.

When did Pyrex stop using borosilicate?

Pyrex stopped using borosilicate glass in the 1950s. The exact year when Pyrex stopped using borosilicate glass is not clear, but it is known that Pyrex switched to tempered soda-lime glass at some point in the past several decades. According to a representative at Corelle Brands, the manufacturer of Pyrex, Pyrex glassware has been manufactured from heat-strengthened soda-lime glass since the 1950s. In 1998, Corning sold the Pyrex brand to World Kitchen LLC, which stopped using borosilicate glass and started using soda-lime glass.

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Richard Charpentier is the CEO of Baking Innovation, a leading provider of baking solutions. He has over 20 years of experience in the baking industry and has been a driving force behind the company's success.