Pyrex Glass Food Storage Containers

Pyrex is one of the most recognized names in glass food storage, but there is an important material distinction between vintage Pyrex and most Pyrex sold in the US today. The original Pyrex, developed by Corning in 1915, was made from borosilicate glass — a formulation that incorporates boron trioxide into the silica matrix, dramatically reducing thermal expansion and making the glass highly resistant to thermal shock. This is why laboratory glassware and vintage Pyrex could go from freezer to oven without shattering.

Most Pyrex sold in the US today uses tempered soda-lime glass rather than borosilicate. The brand was sold and the formula changed; European Pyrex (sold under a different licensing arrangement) still uses borosilicate. US tempered soda-lime Pyrex is significantly stronger than untreated glass and can handle moderate temperature transitions, but it does not have the thermal shock resistance of borosilicate. Taking a cold US Pyrex container directly from the freezer to a hot oven is a risk — the glass can shatter from thermal stress. Allowing the glass to come to room temperature first before oven use is the safety practice.

The glass body of Pyrex — regardless of whether it is soda-lime or borosilicate — is completely inert for food storage. Glass does not leach any compounds into food. It can be safely used in the microwave, oven (with temperature transition care), freezer, and dishwasher without material degradation or food contamination concerns.

The plastic lids that ship with most Pyrex sets are the component requiring attention. Over time, plastic lids can scratch, stain, and degrade — and the food contact surface of a scratched plastic lid has more surface area for leaching than a new lid. Silicone replacement lids are available for standard Pyrex sizes and eliminate the plastic food contact concern while maintaining the excellent glass body as the primary storage surface.