If the logo is in upper case lettering, PYREX, it's most likely made of borosilicate, and thus safer. The lowercase lettering is most likely made of soda-lime glass, so take extra care after any high-heat cooking.
Thickness and Weight: Older Pyrex made of borosilicate glass is generally thicker and heavier than the newer soda-lime glass versions (1). Branding: Look for the uppercase ``PYREX'' logo on the cookware. This indicates that it is made of borosilicate glass, which is more heat-resistant and durable (2).
If it's all caps Pyrex, it's vintage, made of borosilicate. If it's lowercase Pyrex, it's new. And it's soda lime. You still have to be careful.
Pattern. Patterned Pyrex—such as the 1956 Pink Daisy or the 1983 Colonial Mist—tend to be valuable as a collector's item. Other popular patterns include the 1957 Butterprint, which features an Amish couple and their crops, and has been valued at a few hundred dollars.
Cookware with lowercase logos are usually made of soda-lime glass and should not be heated up in the oven or microwave to minimize risk of them breaking. Cookware with logos in all-caps are typically made of borosilicate glass and can be heated at high temperatures without harm.
If it breaks, it's also designed to shatter into tiny, less-dangerous pieces, like a car windshield. But vintage Pyrex is actually made out of an even stronger type of glass, and this difference has some key implications for use, care, and even safety.
Corning has licensed out the use of their PYREX® (upper case lettering) and pyrex® (lower case lettering) logos to 2 different companies. They are not the same products!
Pyrex dishes also hide a little secret code: Many contain a three- or four-digit number that corresponds to a specific dish. A series of Mixing Bowls will feature 401 (1.5 pint), 402 (1.5 quart), 403 (2.5 quart), 404 (4 quart). The iconic two-quart green-and-white casserole dish is a 232.
The Dot Bowls is one of the most popular Pyrex patterns. Released in 1968, the first three Dot Bowls came in orange, yellow, and blue, with green added a year later due to the popularity of the pattern.
This change was justified by stating that soda–lime glass has higher mechanical strength than borosilicate—making it more resistant to physical damage when dropped, which is believed to be the most common cause of breakage in glass bakeware. The glass is also cheaper to produce and more environmentally friendly.
As long as you follow the same guidelines above, vintage Pyrex is A-OK to go in the oven and can be used in oven temperatures up to 425ºF (and skip the broiler). There is one caveat to using your vintage Pyrex, though: Do not use any vintage dishes that are chipped or cracked—in the oven or otherwise.
So What's the Difference? The short answer is: not that much! Both brands can go into the oven up to 425 degrees F (200 degrees C), recommend using trivets when moving from hot to cool surfaces, and come in a variety of shapes and sizes at affordable prices. It really just depends on which one you like more.
How can you tell if a piece is real vintage Pyrex? The secret is simple—check the logo. If the brand name is in all capital letters, it's vintage Pyrex. If it's all lowercase, it's modern.
“The most rare Pyrex patterns are the promotional Pyrex,” says Lucie Courchesne of LucysMidCentury. Promotional Pyrex patterns were sometimes referred to as “non-standard” and were usually offered for a limited time. The company often marketed them as gifts for holidays.
It's tempered, meaning it's been heated and cooled in a manner that makes it more durable under future temperature fluctuations. It's less likely to break under an impact, and when it does, tempered glass breaks into diamond-like cubes instead of long, pointy shards, so it's a little safer to deal with.
Decorative patterns are also key to determining the glassware's value. Lucky in Love, a sweet pink and green design, is prized for its rarity and promotional production. Wright notes that Amish Butterprint, Pink Gooseberry, Snowflake Blue, Crazy Daisy and Friendship are also considered valuable in the Pyrex community.
Vintage Pyrex Stamp and Logo
Flip over your piece and look at it carefully. It will have a stamp that can help you date it: 1940s and 1950s - The oldest Pyrex markings should be on the bottom of glass pieces and feature Pyrex in all capital letters inside a circle with CG for Corning Glassworks.
The naming of these new pieces as "Cinderella" likely had much to do with the popularity of the Cinderella story current at the time both in film and on Broadway. Corning marketers also hoped the underlying theme of a coveted glass object would have a subliminal effect on consumers.
If the logo is in upper case lettering, PYREX, it's most likely made of borosilicate, and thus safer. The lowercase lettering is most likely made of soda-lime glass, so take extra care after any high-heat cooking.
What Makes Pyrex Special. "Pyrex continues to hold its value because most of us associate it with memories of family and holiday gatherings and memories from their childhood," Wright says. "The vintage designs and patterns of Pyrex evoke a nostalgia, which adds to its value for collectors.
This can be tested by heating a small piece of glass and observing how much it expands. Weight: Borosilicate glass is generally denser and heavier than soda-lime glass. Clarity: Borosilicate glass is known for its clarity, while soda-lime glass can have a slight green tint.
Quality glassware tends to have a thicker feel, indicating its sturdiness. It should also have excellent clarity, allowing you to appreciate the color and texture of your drinks. Rim Quality: Pay attention to the rim of the glass. It should be smooth and even, ensuring a comfortable drinking experience.
A pontil, a solid metal rod usually tipped with hot glass, is applied to the base of a vessel to hold it while the mouth is being formed. A pontil mark or pontil scar is the ring-shaped mark left on the bottom the piece when this rod is removed.
You can often tell quality by gently tapping the glass. High-quality crystal glass has a clear “ping” sound, while regular glass has a duller sound.