If it's all caps “PYREX,” it's vintage, made of borosilicate. If it's lower case “pyrex,” it's new, and it's soda lime. (In Europe, Pyrex is still made of borosilicate. So these recommendations only apply to Pyrex in the United States.)
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.
Pyrex products were made of borosilicate glass until the 1950s. At that point, they switched to manufacturing products with tempered soda lime instead. Today, every piece of bakeware made in the U.S. uses tempered soda lime, including the full line of Pyrex consumer glassware.
Pyrex® is borosilicate glass which differs from other glass types as it possesses unique properties of high resistance to chemical exposure, thermal expansion and thermal shock. This has advantages in laboratory uses, a key one being where glassware is directly heated, in beakers, test tubes or flasks.
High thermal resistance: Borosilicate glass can withstand temperature changes without cracking, making it perfect for boiling water. Chemical stability: It is resistant to chemical corrosion, ensuring that it does not leach chemicals into the water when heated.
Borosilicate glass is sold under various trade names, including Borosil, Duran, Pyrex, Glassco, Supertek, Suprax, Simax, Bellco, Marinex (Brazil), BSA 60, BSC 51 (by NIPRO), Heatex, Endural, Schott, Refmex, Kimax, Gemstone Well, United Scientific, and MG (India).
The differences between Pyrex-branded glass products has also led to controversy regarding safety issues—in 2008, the U.S. Consumer Product Safety Commission reported it had received 66 complaints by users reporting that their Pyrex glassware had shattered over the prior ten years yet concluded that Pyrex glass ...
Anchor Hocking has been manufacturing tempered soda-lime-silicate bakeware for nearly 40 years. Prior to that time, annealed borosilicate glass bakeware was the standard.
Yes, borosilicate glass is completely safe for health, as it is non-toxic and does not leach chemicals into food or drinks. It is a safer option as compared to regular glass due to its resistance to thermal shock and chemical or acidity reactions, making it suitable for storing, heating and serving food and beverages.
Tempered Soda Lime. The various formulations for Pyrex glass have been a source of controversy for many, as well as a source of consumer lawsuits over shattering bakeware.
It is stronger than regular glass but it can still break or crack if it is dropped or hit hard. It is important to handle borosilicate glass with proper care to minimize the risk of breakage.
Corning used borosilicate to produce all Pyrex products. However, the company that purchased the cookware products switched to soda-lime glass, adopting the name pyrex (spelled with all lowercase letters).
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.
It could be counterfeit glass! Soda lime and Borosilicate glass look very similar, but perform completely differently. Lately, there has been a rash of counterfeit glass introduced into the glass-gauge industry, some so-called companies even illegally using the corporate names of legitimate glass providers.
The brand, Pyrex, has historically owned the trademark for little-p pyrex, but its parent company, Corning, has since sold it. Lowercase "pyrex" is produced by other cookware companies that don't use the heat-resistant borosilicate glass the original company does (more on that below).
Implications of the Material Change
Consumers are advised to avoid exposing Pyrex soda-lime glassware to extreme temperature changes. In conclusion, the decision by Pyrex to transition from borosilicate to soda-lime glass was driven by cost, durability, and manufacturing efficiencies.
there is no differance in anchor or pyrex they are exactly the same glass soda lime glass.
According to Pyrex's safety and usage instructions, “While the glass is designed for temperatures typically used in baking, it can break when exposed to the direct heat element while the oven is preheating.”
Baking glassware such as Pyrex dishes in usable condition should be donated to local thrift stores or otherwise reused. If unusable they should be thrown away in the trash. They should not be added to curbside recycling. They are made of a different material than glass bottles and jars.
Everyone loves a good kitchen hack, and one of the most popular examples concerns glass cookware. Between Twitter, Reddit, and TikTok, there are hundreds of posts asserting that all-caps PYREX is the good stuff (aka, borosilicate glass), and all-lowercase pyrex is junk (aka, tempered soda-lime glass).
Borosilicate glass is sold under such trade names as Simax, Borcam, Borosil, Suprax, Kimax, Heatex, Pyrex, Endural, Schott, or Refmex, Kimble.
What material is safe? You will want to stay away from metallic and porcelain teaware if you want to prevent toxins from leaching into your tea. And the best material for your teapot is something called borosilicate glass. Borosilicate glass is lead and cadmium-free, and it won't leach harmful chemicals into your tea.