Sometimes I am very absent minded around the kitchen, and that does lead to a few issues. There was a time when I used a cooking pot as a double boiler and the top one just refused to budge.

That day I learnt how to break a vacuum seal. In most cases a vacuum seal happens when the metal expands due to heat and contracts and tightens the pot as it cools.

Breaking A Vacuum Seal

In case the vacuum seal was created while using it like a double boiler, then just reheat the first pot until the water starts to boil again. This way the lower pot will expand again and release the upper pot, thus breaking a vacuum seal. If this trick does not work, then it time to try the cold spray. First remove the food from the top pot and then fill it with cold water. The contact will cool the metal and break a vacuum seal.

There are also times when a vacuum seal is formed while you were storing something in the jar. In that case boil some water and immerse the bottom pot into the hot water. Once the pot warms up it will be able to break a vaccum seal. In case there is still an issue to break a vaccum seal after trying this, continue dipping the lower pot in hot water and place ice cubes on the pot above. This way while one expands the other will contrast thus breaking a vacuum seal. If your water glasses are stuck together, then try this trick.  

Image Credit: allitera.tive.org