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The various uses of borosilicate glass have become a source of joy for many culinary, food, and laboratory scientists.

However, one of the most pressing concerns remains: how to identify Borosilicate glass, especially in today’s world of numerous glass varieties.

This glass type, known for its remarkable thermal resistance and versatility, finds its way into more aspects of our daily lives than we may imagine.

Recognizing Borosilicate glass is more than simply a curiosity; it is a useful skill with consequences for safety and function.

In the subsections that follow, we will break down the essential traits and provide specific procedures for precisely identifying this glass variation.

So, let’s go out on an adventure to learn and differentiate the persistent Borosilicate amidst the glass fabric.


Borosilicate glass often feels smoother and denser compared to regular glass. It has a higher resistance to thermal expansion and can withstand higher temperatures, making it commonly used in laboratory glassware and durable glass products.

The texture may vary depending on its specific composition and any additional treatments applied.


how to identify Borosilicate glass

Here are three ways to identify borosilicate glass:

  • You can identify Borosilicate glass by its exceptional clarity.
  • Get a Glass jar, pour glycerol liquid into it, then take your two samples of a glass tube and immerse one after the other. If one of the glass tubes disappears, then it is Borosilicate glass but if it doesn’t then it is soda lime glass. This serves as confirmation that the refractive index of borosilicate glass is 1.474.
  • Check the density of the glass sample, if the density is around 2.23g/cm3, then it is Borosilicate glass but if not, it is soda-lime glass as the density of soda-lime glass is lower than that of Borosilicate glass.

NOTE: The density (p) of a material, including glass, is calculated using this formula: p = m/v, where m is the mass of the glass and V is its volume.

To get mass: weigh the glass and to get volume: multiply this: length, height, and width of the sample glass then finally divide mass by volume (see the formula above).


How to tell if Pyrex is Borosilicate

The best way to know if your Pyrex is Borosilicate or not is to check when and where it was manufactured and the Logo on the body of the glass product.

For the record, did you know that the glass company Corning marketed Borosilicate glass under the name Pyrex? Yeah, they did.

To bring this home, check your measuring cup in the house, if you see PYREX all in uppercase letters, it simply means it is Borosilicate glass.

Borosilicate glass is hardly susceptible to explosion in the microwave or oven.

PYREX Borosilicate glass

Borosilicate glass can transition from cold to hot temperatures without cracking.

Old PYREX measuring cups were made from Borosilicate glass; Borosilicate glass supports extreme temperatures from negative 40 to 300 degrees Celsius and is resistant to thermal shock up to 222 degrees Celsius.

Old PYREX can go from the Freezer at a temperature of negative 20 degrees Celsius into the oven at a temperature of 200 degrees Celsius.

This quality makes Borosilicate glass suitable for use on a gas stove and other open heat sources.

pyrex soda lime glass

However, if you see pyrex all in lowercase letters, then it simply means it is made of soda lime glass normally has a bluish tint.

Soda lime glass is affordable, has different thermal properties from Borosilicate glass, and is more susceptible to thermal shock.

In addition, Soda lime glass has a lower thermal shock resistance making it prone to explosion in the microwave or oven.

Either in the 1980s or 1990s, the composition of PYREX Borosilicate glass was altered in the United States or they shifted from Borosilicate glass to soda lime glass but in Europe and other countries, PYREX is still made with Borosilicate glass.

In conclusion, PYREX (Logo in uppercase letters) is made of Borosilicate glass, but pyrex (logo in lowercase letters) is not.


PYREX Borosilicate glass simply means that the “glass brand” is made up of “Borosilicate glass” not “soda lime glass”.

Borosilicate casserole cooking pan for Oven

An example of a PYREX Borosilicate glass brand is the Ums Rectangular Glass Baking Tray Dish perfect for cooking, baking, and serving.

They are a 16 X 11 inch – 4 Quart Cooking and Serving Pan, the perfect heat-resistant glass ovenware.

This high Borosilicate glass serving pan is made from high-quality, food-grade glass that is completely safe and free of any toxic or odorous substances.

Volarium Borosilicate glass baking casserole dish

This Borosilicate casserole pan is versatile, allowing you to bake lasagna, pie, bread, brownies, and other delicacies. It also serves as a food storage container for leftovers or meal preparation.

This Borosilicate baking glass pan for the oven is an eco-friendly and sustainable kitchen equipment that may be safely used in the dishwasher, microwave, and refrigerator.

The glass material is free of dangerous chemicals and contaminants, making it a safe choice for you. You won’t have to worry about food, pathogens, odors, or harmful substances leaking into these glass baking dishes.

Others are the Simax Borosilicate Glass Roaster Baking Dish and the Volarium Borosilicate Casserole Glass Baking Dish for Oven.


Yes, Borosilicate glass is freezer-safe because it has a lower coefficient of thermal expansion compared to other types of glass.

This means it can withstand temperature changes without breaking or shattering. The stability of borosilicate glass makes it suitable for use in the freezer, where rapid temperature fluctuations can occur without compromising its structural integrity.

Real Pyrex Logo

The real Pyrex logo typically features a stylized, capital “P” followed by an uppercase letter “YREX” or a stylized, lowercase “p” followed by a lowercase “yrex” in a bold and distinctive font.

The logo is usually clear, well-defined, and consistent. Be cautious if you notice any blurriness, irregularities, or variations in the logo, as these could be indicators of counterfeit products.

Additionally, genuine Pyrex items often have capacity or model numbers alongside the logo for identification.


To avoid buying fake Pyrex, follow these tips:

Check Markings: Authentic Pyrex products usually have clear, consistent markings, including the logo and capacity. Be wary if these details appear blurry or inconsistent.

Material: Real Pyrex is either made of Borosilicate glass or soda lime glass. Borosilicate glass is known for its durability and resistance to thermal shock. While soda lime pyrex cannot withstand rapid temperature changes.

Brand Reputation: Purchase from reputable retailers or directly from the official Pyrex website to reduce the risk of buying counterfeit products.

Packaging: Examine the packaging for signs of authenticity. Genuine Pyrex typically comes with clear and professionally printed packaging, while counterfeit items may have cheap or poorly printed packaging.

Price: If the price seems too good to be true, it probably is. Be cautious of significantly lower prices compared to reputable sellers.

Research the Seller: Check reviews and ratings of the seller, especially if buying online. Reputable sellers are less likely to carry fake products.

Know the Product Range: Be familiar with the designs and styles of authentic Pyrex products. Counterfeit items might have subtle differences in patterns or shapes.

By being vigilant and considering these factors, you can increase the likelihood of purchasing genuine Pyrex products.


See below the various physical characteristics of Borosilicate glass:

  • They are clear and have a smooth surface
  • They are not too heavy or not too light
  • Borosilicate glass has good chemical durability and transparency, making it ideal for various applications, including scientific instruments and cookware.
  • They come in various shapes and sizes depending on your needs.
  • Borosilicate glass has a high thermal resistance and low coefficient of expansion. It can withstand sudden temperature changes, making it suitable for laboratory glassware and certain kitchen products.


You can purchase Borosilicate glass products from various sources, including:

Specialty Glassware Stores: Shops that focus on laboratory equipment or specialized glassware often carry Borosilicate glass products.

Online Retailers: Platforms like Amazon, eBay, or specialty online stores offer a wide range of Borosilicate glass items, from cookware to scientific glassware.

Kitchenware Stores: Some high-end kitchenware stores may carry Borosilicate glass cookware.

Craft and Art Supply Stores: Borosilicate glass rods and tubes are used in glass art, so stores catering to artists may have supplies.

Local Specialty Shops: Check with local shops that specialize in glassware or scientific equipment.

Ensure that the product specifications explicitly mention Borosilicate glass to ensure you’re getting the desired material.


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