You’re probably looking at a glass baking dish with “Pyrex” printed on the bottom and another one with “PYREX” in bold uppercase letters. Now you may be thinking, “Are these two different?” “Is one safer than the other?” “Am I going to blow up my lasagna?”
I have seen the panic, I have read the many online posts, and yes, the difference between them does exist. However, it is not as scary as many parts of the Internet want you to believe.
The reason there is a difference between Pyrex and PYREX lies in the type of glass that is being used and where the glass was manufactured, not just the logo.
Let us break down what you need to know.
What Is Pyrex? (Lowercase)
If you have purchased any glass baking dishes, glass measuring cups, etc. in the United States over the last several decades, chances are you have Pyrex with a lower case “P”. This type of Pyrex is made from tempered soda-lime glass. Tempered glass is selected for its strength and impact resistance.
Plainly speaking, it will survive drops much better than its predecessor. I have personally dropped mine on the kitchen counter, and it bounced back (although I would not recommend trying that).
Soda-lime glass, however, is not as tolerant of rapid changes in temperature. For example, pouring boiling water into a cold glass dish or taking a dish directly from the freezer to the oven could create problems. You could literally burn yourself. Nonetheless, if used correctly, i.e., without extreme temperature shocks, it is perfectly safe to use for common household cooking tasks.
What Is PYREX? (Uppercase)
PYREX in all capital letters refers to glassware made from borosilicate glass, which was originally developed for laboratory use. Borosilicate glass is far superior in terms of handling thermal shock. It can easily transition from an extremely cold state to an extremely hot state without breaking.
That’s why borosilicate glass continues to be used today for laboratory beakers, test tubes, etc., and for some foreign brands of cookware. I have personally worked with laboratory equipment, i.e., beakers and test tubes, made from PYREX glassware that has been subjected to both flame and freeze temperatures without failing.
However, borosilicate has a weakness. While it is excellent for dealing with extreme temperature changes, it is also more prone to damage due to dropping. A borosilicate glass dish dropped will probably crack, whereas a soda-lime glass dish dropped will probably survive.
Why the Difference Exists
All of this confusion began when Corning, the original manufacturer of Pyrex, sold off the consumer kitchenware portion of its business many years ago. As a result of licensing agreements, the same product was being produced by various companies in different areas of the world. In the United States, World Kitchen (now Instant Brands) switched to producing Pyrex kitchenware from soda-lime glass.
In contrast, some producers of glassware continued to produce PYREX glassware in Europe and elsewhere using borosilicate glass. The decision to continue using borosilicate glass was purely based upon regional production methods and varying levels of compliance with regional health regulations and safety standards.
Therefore, it is not a scam; it is simply branding and the results of differences in the application of materials science.
A Safety and Performance Comparison
To put this into perspective:
- Heat Resistance: PYREX (borosilicate) wins. It can withstand extreme temperature fluctuations.
- Impact Resistance: Pyrex (soda-lime) wins. It is less likely to chip or crack if dropped.
- Typical Usage: Pyrex is well suited for casserole dishes and baking dishes. PYREX is ideal for laboratory applications and/or recipes that involve extreme temperature changes.
Both are completely safe. They are simply different tools for different purposes. It’s similar to choosing between a chef’s knife and a paring knife, you need to know what you’re working with.
How to Determine Which Type You Own
Your best indicator is the logo: lowercase “pyrex” generally indicates soda-lime glass, while uppercase “PYREX” typically indicates borosilicate glass. However, this is not foolproof.
There are instances where a product with an all capital letter logo is soda-lime glass, while a product with a lower case logo is borosilicate. Crazy, right? Your safest bet is to check the country of origin. Products produced in Europe are more likely to be borosilicate glass. Products produced in the USA are almost always soda-lime glass.
Additionally, laboratory glassware is essentially always borosilicate glass. Therefore, if you are using borosilicate glass in a laboratory setting, you are good to go.
Which Should You Choose?
If you are a homeowner looking for durable and dependable glass baking dishes that will not shatter if you sneeze too loudly, choose Pyrex (soda-lime). It is suitable for common household use and will work perfectly.
If you bake with extreme temperature variations, or if you enjoy knowing your glassware can endure more dramatic temperature swings, choose PYREX (borosilicate). Just do not drop it.
Regardless of whether you own Pyrex or PYREX, the glassware is perfectly safe provided you follow proper use instructions. That is the most important point.
Myth Busting Regarding Pyrex vs PYREX
Time to debunk some Internet drama!
“Lowercase Pyrex explodes!” No, it does not randomly explode. It will only explode when you misuse it, such as putting it in the freezer, then immediately placing it in the oven. Simply follow the usage recommendations, and it is as safe as any other type of glassware.
“PYREX is always better!” Not necessarily. While borosilicate glass is better for handling extreme temperature changes, it is also more delicate in other ways. I have seen many people treat their PYREX glassware gently, as they are fearful of causing a chip or crack.
The Internet loves a good scare story, but ultimately both types of glassware are perfectly fine when used appropriately.
Therefore, the main difference between Pyrex and PYREX is simply the type of glass it is made from, either soda-lime or borosilicate. It is simply branding and the application of materials science.
Do not let fear-mongering control your choices. Simply utilize your glassware as intended, and you will be fine.
