Freezing glass lunch boxes works — just don't shock the glass

Freezing glass lunch boxes works — just don’t shock the glass.

Yes, you can freeze a glass lunch box, and it’ll be fine as long as you don’t yank it between extreme temperatures.

Most glass lunch containers are either tempered or borosilicate glass, and both are freezer-safe. The cold itself won’t hurt them. What kills glass is thermal shock — that sudden crack you get when hot glass hits cold water, or frozen glass hits something hot. So the freezer is fine; the microwave right after is where people mess up.

A few ground rules. Leave an inch of headroom because food expands when it freezes, especially liquids and soups. Let it thaw in the fridge overnight or on the counter for a bit before reheating. And if you’re going straight from freezer to microwave, don’t blast it on high — thaw it first or use a lower power setting.

One more thing: check for chips or cracks before freezing. Glass that’s already damaged is far more likely to shatter with temperature changes. If it’s in good shape, you’re good to go.

The glass can handle the cold — just don’t ask it to handle the cold and the heat at the same time.