Prevent a vacuum seal on your pots by cooking with the lid sitting slightly askew so that a vacuum does not form.
Slide the flat blade of a metal spatula between a cooled lid and pot. Once the smallest breach is made in the vacuum, the pot lid should come off easily.
A weak seal can sometimes be broken once the pan cools down.
Sometimes you want to tightly seal a lid to its container, such as when you're canning foods. The vacuum seal created inside the contain as the contents cool down after being heated in the water bath or pressure cooker prevents spoilage and allows for long-term storage. The same thing can happen when you cover a cooking pan with a tight-fitting lid, then turn down the heat. When the lid inadvertently seals to the pan, it creates a problem, but breaking this seal should be a simple matter.
Put the sealed pan back on the burner.
Heat the pan slowly on low so that the air inside the pan warms and expands.
Wait for the seal to break. The lid should lift off without effort once the heated air inside expands.
In 2007 Nannie Kate discovered that the words she had been writing all her life had an actual cash value. She's been writing professionally through brokers ever since. With an English major background she creates articles and ebooks on a wide variety of subjects.