Snap-lock glass boxes leak soup. Test them before you trust them.

Glass lunch boxes with snap-lock lids are not truly leak-proof for soups — most will dribble or spray when handled. That seal is a thin rubber gasket, and it only works when the lid clamps down evenly. Soups are thin and oily, so they find every millimeter of gap you thought was sealed.

Hot soup makes it worse. When you seal hot liquid and then refrigerate it, the pressure changes inside the box, which can suck the seal inward or push liquid out over time. Same thing happens when you microwave without loosening the lid. So “leak-proof” in the marketing means “leak-proof in a vertical position without any temperature change,” basically.

Test any box before you trust it: fill it with warm water and a drop of dish soap to break surface tension, close it, shake it hard for ten seconds, then set it upside down on a paper towel for ten minutes. Also press down on each corner to see if air or water escapes — that’s where cheap seals fail. If the paper towel is dry, you’re fine.

A final tip: if you’re planning to carry soup in a bag with a laptop or paperwork, wrap the box in a plastic bag anyway. Future You deserves that insurance.