What it is
Glass is primarily silicon dioxide fused with additives that determine its thermal properties.
Borosilicate glass adds boron oxide for superior thermal-shock resistance; soda-lime glass is cheaper but more prone to shattering under temperature change.
Why it matters
Nothing leaches from properly manufactured glass at cooking, freezing, or storage temperatures.
It is transparent, easy to inspect, and does not carry the odours or stains that plastic accumulates.
The main risk is mechanical: modern soda-lime Pyrex is more prone to thermal shock than pre-1998 borosilicate Pyrex.
Common uses
- Bakeware — pie plates, casserole dishes, loaf pans
- Food storage containers and jars
- Water bottles and baby bottles
- Blender jars and beverage carafes
Safety considerations
- Avoid extreme thermal shock — do not place a hot glass dish on a cold surface or add cold liquid to a hot dish.
- For baby bottles, choose borosilicate where possible; the extra thermal resilience is worth the small premium.
- Painted or decorated glassware can contain lead pigment — a concern for the decoration, not the glass itself.
Where you meet it in the home
- Kitchen — bakeware, storage, drinkware
- Nursery — baby bottles and sippy cups
- Bathroom — jars and dispensers
Related categories
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Frequently asked questions
Is new Pyrex safe?
Yes for oven-to-table baking within manufacturer instructions. Avoid moving it between temperature extremes.
Borosilicate vs soda-lime — does it matter?
Borosilicate handles thermal shock better; soda-lime is more affordable but more fragile to temperature change. Prefer borosilicate for baby and hot-liquid use.
Editorial references
- FDA — Guidance on food-contact materials
- ASTM C1464 — Bent glass thermal properties
Last updated 2026-07-18.