Double crystal glass lid can not open, how to do?

Double crystal glass cup lid almost impossible to open, the special circumstances can not open, please do so:

1. balance the internal and external atmospheric pressure. Let the cup go back to its original state. It is to soak for 8-10 minutes in the boiling water of 90 degrees.

2. increase the friction between the handle and the cup cover. Wet the blanket with a damp towel.

3. or a cup, knock down a few times.