Freezing looks gentle, but two forces break things in the freezer: expansion (water grows about 9% as it freezes, so a full sealed container can crack or burst) and thermal shock (glass that goes from warm to freezing too fast can shatter). Get the headspace and the cooling right and most containers freeze fine.
Freezing without cracks or bursts
- Leave headspace. Liquids and wet foods expand — leave roughly an inch at the top so the container isn’t stressed from inside.
- Cool before you freeze. Let hot food come down to room temperature (or refrigerator-cold) first to avoid thermal shock on glass.
- Choose freezer-rated glass. Straight-sided, wide-mouth jars marked freezer-safe resist cracking far better than narrow-shouldered ones.
- Watch for freezer burn. Air is the enemy of quality — press out air or use freezer bags for long storage.
Common containers in the freezer
| Item | Verdict | Why / condition |
|---|---|---|
| Freezer-safe plastic containers | Safe | Made for it; leave headspace for liquids. |
| Mason jars | Conditional | Use wide-mouth, freezer-safe jars with headspace; fill below the shoulder. |
| Regular drinking glass | Unsafe | Thin, narrow glass cracks from expansion and shock. |
| Glass baking dish (tempered) | Conditional | Freeze cooled food only; never move it straight to a hot oven. |
| Freezer / zip bags | Safe | Great for flat, air-free storage. |
| Aluminum foil | Safe | Fine in the freezer; double-wrap to limit freezer burn. |
We’re adding a page for each container and food, with the exact headspace and cooling steps. Tell us what you want to freeze.
General guidance — check your label. Verdicts here are based on manufacturer specs, USDA/FDA guidance, and material science, but individual products vary by line and generation. Always defer to the symbol or care instructions printed on your specific item. When in doubt, don’t heat it.