When playing with soap bubbles in a bathtub, it seems impossible to bring two bubbles together to form a single larger bubble. When two floating bubbles meet, a wall is formed between them. Even when pressure is applied from both sides, they refuse to merge. Attempts to break the wall from below using my finger also always fail. I can even move my finger through the wall from one bubble to the other but no merging ever takes place. The bubbles easily pop when poked from outside, but don't seem to want to pop into each other. This seems to be true even when the bubbles are of different size.
So my question is twofold
Why can't I get two bubbles to merge?
Is there anything that I can do to force the two bubbles to merge?
I've read that bubbles minimize surface area, so my thinking is that this has something to do with it, but I don't understand how. It seems to me that joining the two bubbles would result in a smaller surface area than the two joined together, but I could be wrong. I also thought the internal pressure of the bubbles might play a role.