How to remove air bubbles from snow globes?

I am repairing a snow globe and have only one problem I can't seem to remove the bubble. Does anyone know how to remove the air bubble in the snow globe when reassembling? I don't want to have to poke a hole in the rubber gasket and then reseal with silicone. We've tried adding water but doesn't seem to work. What else can we try. I wish someone would write a book on snow globes including repairs and where to purchase accessories.