Opening stuck lids. A partial vacuum in jars and bottles helps the lid form an airtight seal and keep food fresh. But the vacuum also makes lids difficult to unscrew. If you don’t plan to reuse ajar, punch a hole in the lid with a can opener or ice pick to break the seal. A slight vacuum also forms when you place ajar with warm food in the refrigerator. To help break the seal, run warm (not hot) water over the jar before opening it.
To get a better grip on a stuck lid, wrap rubber bands, a damp sponge, or a dish towel around it. Or use one of the widely available nonskid rubber pads. You can also get viselike metal jar openers with teeth and long handles. Pliers will open a small lid.
To keep a lid from sticking, wipe all food from it and the jar rim. If dried food does seal a lid, tap gently around its edge with a knife handle. Or run warm water over the lid; heat softens the food and expands the lid, letting you unscrew it.